Vol. 15 No. 3 July 1995



This issue contains a heavy emphasis on the Vet Notes because there has been some recent activity that is quite timely. The issue of the use of clenbuterol in show animals is particularly important at this time of year with the county and state fairs starting soon. The bottom line message to producers is: Don’t Use It! You will get caught if you win! In this issue we also present an article written by Dr. Allan Felsot, Extension Toxicologist for Washington State University, and hope to borrow more of his work in the future. After having received a number of questions about oleander leaves in compost, Environmental Toxicology Administrative Assistant (and production manager for this newsletter) Sandy Ogletree suggested that we include a new column on "Frequently Asked Questions" (FAQs), which debuts in this issue. We welcome input from county advisors for both questions and answers to FAQs they receive which relate to environmental toxicology.

Long-term Exposure to Chlorine Results in Nasal Irritation But Not Cancer in Mice and Rats

Chlorine is a highly reactive, water-soluble gas widely used in cleaning agents, disinfectants, water purification, bleaching, and the manufacture of numerous compounds such as plastics. Not unexpectedly, the very properties of reactivity and solubility that have made chlorine hygienically and industrially indispensable are also responsible for its toxicity.

Substantial human data are available on acute irritation from short-term exposure to chlorine. These data, along with complementary information from short-term animal studies, were used to set 0.5 ppm as the threshold limit value expressed as a time-weighted average (TLV-TWA) that is currently used for the protection of workers. However, questions still remain about whether long-term, low-level exposure to chlorine can cause cancer or adversely affect health in other ways.

To address these questions, CIIT (Chemical Industry Institute of Toxicology) researchers conducted a study in which female and male mice and rats were exposed to chlorine gas at concentrations of 0.4, 1.0, and 2.5 ppm for up to two years. Chlorine did not affect the survival of exposed animals and did not cause cancer. A number of noncancerous lesions were observed in the nasal passages of both mice and rats, but the most severe lesions were confined to the front part of the nose. No lesions were observed in the larynx or lower respiratory tract, and chlorine exposure did not affect any other organ system. Female rats were much more sensitive to chlorine gas than male rats, while female mice were less sensitive than male mice. In previous studies, female and male animals have also responded differently to chlorine exposure, which has alerted researchers to the possibility of sex differences in humans as well.

As demonstrated by this study, airborne chlorine is an irritant to the upper respiratory tract of mice and rats but is not carcinogenic. In using rodent data to assess the risk to human health from continual low-level exposure to chlorine, differences between rodents and humans in the uptake and distribution of chlorine at various sites in the respiratory tract must be taken into account. Mice and rats, who are obligate nose breathers and have a more complex nasal structure than humans, frequently develop more severe nasal responses to airborne toxicants at a given exposure concentration than do monkeys or humans. One of the goals of CIIT’s respiratory toxicology program is to better understand and measure species differences so that the results of animal testing can be used more confidently in setting safe human exposure limits.

Wolf, D. C., Morgan, K. T., Gross, E. A., Barrow, C., Moss, 0. R., James, R. A., and Popp, J. A. (1995). Two-year inhalation exposure of female and male B6C3FI mice and F344 rats to chlorine gas induces lesions confined to the nose. Fundamental and Applied Toxicology 24, 111-131.

REF: Chemical Industry Institute of Toxicology IMPACT, March 1995.


Wok cooking, particularly with unrefined Chinese rapeseed oil, has been implicated in epidemiologic investigations of lung cancer among Chinese women, National Cancer Institute researchers and others reported in the June 7 issue of the Journal of the National Cancer Institute.

Volatile emissions from unrefined cooking oils are mutagenic and scientists have set out to identify and quantify the potentially mutagenic substances emitted from a variety of cooking oils heated to the temperatures typically used in wok cooking. Oils tested were unrefined Chinese rapeseed oil, refined U.S. rapeseed (known as canola), Chinese soybean and Chinese peanut. The researchers also tested linolenic, linoleic and erucic fatty acids.

1,3-butadiene, benzene, acrolein, formaldehyde and other related compounds were qualitatively and quantitatively detected, with emissions tending to be highest for unrefined Chinese rapeseed oil and lowest for peanut oil. The emissions of 1,3-butadiene and benzene were approximately 22-fold and 12-fold higher, respectively, from heated unrefined Chinese rapeseed oil than from heated peanut oil. Lowering the cooking temperatures or adding an antioxidant such as butylated hydroxyanisole before cooking decreased the amount of volatile emissions.

Among the individual fatty acids tested, heated linolenic acid produced the greatest quantities of 1,3-butadiene, benzene and acrolein. Condensates from heated linolenic acid, but not linoleic or erucic acid, were highly mutagenic.

U.S. Cooking Oils Refined, But Further Studies Needed: Researchers

"These studies, combined with experimental and epidemiologic findings, suggest that high-temperature wok cooking with unrefined Chinese rapeseed oil may increase lung cancer risk. The common use of wok cooking in China might be an important but controllable risk factor in the etiology of lung cancer. In the United States, where cooking oils are usually refined for purity, additional studies should be conducted to further quantify the potential risks of such methods of cooking."

Lung cancer incidence in Chinese women is among the highest in the world, but tobacco smoking is not a major risk factor among Chinese women.

Data from other studies are limited, but volatile emissions from several cooked foods (e.g., beef) have previously been found to be mutagenic, as were samples of restaurant kitchen air. Furthermore, some studies in western countries indicate that restaurant cooks have elevated risks of lung cancer, even when risks are adjusted for tobacco use."

U.S. Canola Oil Is Not Mutagenic, May Contain Oxidation Inhibitors: Study

"The presence of linolenic acid does not fully explain the mutagenicity results because Chinese rapeseed oil is mutagenic, while U.S. canola oil is not, although they have similar linolenic acid contents."

At exposures as low as 6.5 ppm, 1,3-butadiene is a lung carcinogen in laboratory mice. Benzene and formaldehyde have also been linked to lung cancer, but human studies are lacking on acrolein, the researchers said.

1,3-butadiene has been reported at levels ranging from 19 micrograms to 75 micrograms per cigarette in mainstream smoke, depending on whether the cigarette smoke is filtered, but the amount generated from heating Chinese rapeseed oil was approximately 0.6 micrograms. The lifetime exposure to 1,3-butadiene, benzene, acrolein and other detectable volatile compounds from wok cooking "appears to be substantially less than that for a heavy smoker. However, these calculations may underestimate the exposure and risk because they do not sufficiently consider peak exposures during the initial generation of volatile compounds."

To reduce exposures, the researchers recommended cooking at lower temperatures, adding antioxidants, hydrogenation during refining and increasing ventilation during cooking.

REF: Food Chemical News, 37(16), June 12, 1995.


Cancer epidemiologists should be aware of the limitations of biomarkers and cross-check these findings against more straightforward methods, such as questionnaires, records and environmental monitoring, according to a commentary appearing in this month’s issue of their journal Epidemiology.

Researchers argued that there are "considerable limitations to the use of biomarkers of exposure in cancer epidemiology studies, that the current overemphasis on this approach is misplaced, and that biomarkers have both strengths and limitations relative to other methods of exposure assessment."

Aflatoxin Urinary Biomarkers’ Association with Elevated Cancer Risk One of Few Success Stories

Urinary biomarkers of aflatoxin exposure were shown to be associated with elevated cancer risk in research reported in 1992.

"Although these markers only reflect recent exposures, it is likely that they provide a better measure of historical aflatoxin exposure than is provided by personal interviews or market surveys of contaminated food stocks, since the level of contamination varies greatly, owing to temporal and local factors."

But researchers said one of the major limitations of biomarkers is that they only indicate relatively recent exposures. Even the best markers of chemical exposures, said the journal, reflect only the last few weeks or months of exposure.

Historical information on exposure surrogates will often be more valid than current direct measurements of exposure or dose.

While more valid and inexpensive biomarkers may be developed, some inherent problems with biomarkers cannot be overcome, the journal said. One example is the dilemma of choosing the wrong biomarker, which may be why a specific dietary micronutrient that prevents cancer cannot be found in green and yellow vegetables.

While cancer assessment is experiencing a "comparable revolution in methods of exposure assessment," the authors cautioned researchers to assess the strengths and weaknesses of these new tools.

REF: Food Chemical News, 37(2), March 6, 1995.

Organophosphorus insecticides and delayed neuropathy

In a prime-time CBS report several months ago, the safety of chlorpyrifos following nonoccupational exposures was called into question. The issue, possible occurrence of a neurotoxic syndrome called delayed neuropathy, probably has more significance to the public than the Alar controversy did because chlorpyrifos in its various formulations (e.g., Dursban, Lorsban) is the most widely used insecticide in the United States and can be sold in garden stores to homeowners.

Washington State University pesticide applicator training programs emphasize the extreme hazard of occupational exposures to organophosphorus (OP) insecticides, which include chemicals such as chlorpyrifos, dimethoate (Cygon), azinphos-methyl (Guthion) and mevinphos (Phosdrin). Safety is gained by using protective clothing. But what is the hazard to the homeowner who has just had his house treated with Dursban to control cockroaches?

First, it is necessary to distinguish the rare syndrome known as delayed neuropathy from the kinds of poisonings that applicator’s can experience when the chemical is mishandled or protective gear is not used. All OP insecticides inhibit the nerve enzyme called acetyl-cholinesterase (AChE), which is essential in modulating nerve impulse transmissions between nerve fibers. Without enough properly functioning AChE, nerves fire uncontrollably, ultimately leading to respiratory failure. Nonlethal symptoms of OP poisoning include nausea, vomiting, abdominal cramps, diarrhea, excessive salivation, headache, dizziness, pinpoint pupils, blurred vision, muscle twitches, difficulty breathing, random jerky movements and convulsions.

The most hazardous OP compounds are those with oral and dermal LD50s <50 mg/kg. These numbers refer to the effects resulting from inhibition of acetylcholinesterase (called cholinergic poisoning) after administration of a single dose. The LD50 (the dose lethal to 50% of a test population) can be found on Material Safety Data Sheets that manufacturer’s are required to supply with any chemical product. Chlorpyrifos is considered moderately toxic with an oral LD50 ranging from 82-245 mg/kg and a dermal LD50 of 202 mg/kg. The acceptable daily intake (ADI) for chlorpyrifos (i.e., the daily dose that causes no observable effect in animal toxicity tests and adjusted downward with a 100-fold safety factor) is 10mg (micrograms)/kg body weight/day. Tolerances for pesticide residues in food are set at levels that will not exceed the ADI.

The symptoms and causes of delayed neuropathy (also called OP Induced Delayed Neuropathy or OPIDN) are unique when compared to cholinergic poisoning. First, whereas all OP insecticides inhibit AChE, only a few have been found to cause OPIDN. For example, dimethoate does not cause OPIDN, but several OPs whose registrations have been suspended are definitely known to cause the syndrome; these include EPN and leptophos. Second, the occurrence of the OPIDN syndrome is tested primarily using hens as opposed to rats; the hen is considered a more sensitive indicator. The symptoms occur 10 days to several weeks following treatment and is characterized by loss of muscular coordination in the limbs which could lead to paralysis; the syndrome is not reversible and no proven remedy exists. The purported mechanism of toxicity is a breakdown in the insulation around the nerve fibers and an associated die back of the tissue. An enzyme in the fibers, known as neuropathic target enzyme (NTE) is inhibited by certain OPs, but how the biochemical effect translates to destruction of the nerve tissue is unknown.

The effect of insecticide dose on the onset of OPIDN and the determination of a no-observable-effect level (NOEL) has been carried out for many OPs because the test is required for registration of pesticides whose primary mode of action is on the nervous system. Hens are usually given a single sublethal oral dose or multiple small oral doses over many days. The hens must live because the determination of OPIDN depends on observations of changes in their gait. Many OPs are toxic, and doses that are not lethal to the hens do not produce OPIDN. To overcome these limitations, researchers can administer amounts of insecticide larger than the lethal dose by giving the hens antidotes to keep them alive. By this method, one experiment has shown that a single oral 90 mg/kg dose of chlorpyrifos can cause OPIDN in hens (the LD50 was 32 mg/kg). In another study, OPIDN-like symptoms were produced after feeding hens a 20 mg/kg dose for 20-28 days, but the effects were reversible and thus not considered to be a true OPIDN syndrome. A confirmed case of OPIDN associated with chlorpyrifos has been reported in humans following an attempted suicide, i.e., a high dosing incident.

Whether or not chlorpyrifos can induce OPIDN obviously depends on dosage, and the only testing done produces artificially high body burdens by using antidotes to keep the test hens alive. Given the current state of knowledge about pesticide residues in food, that consumed doses would even come close to the levels that might cause OPIDN is nearly impossible. But what about nonoccupational exposures that might take place in the home after a cockroach spray? Some studies have monitored air residues of chlorpyrifos after a typical indoor application; one worst-case study of an unventilated room eight hours after application had airborne chlorpyrifos concentrations of 94 mg/m3. For an exposed 10-kg child, this concentration translated to a dose of 158 mg/kg. The single dose NOEL for chlorpyrifos in humans is 500 mg/kg. In a ventilated room, the estimated exposure was halved, further increasing the margin of safety. Most published studies show that airborne residues are well below 50 mg/m3. Bear in mind that the NOEL refers to cholinergic effects, not OPIDN; based on hen studies, the NOEL for OPIDN would be much higher.

Seven million individual applications of Dursban are estimated to be made each year; yet, the number of complaints about poisonings averages less than 30 per year. Despite this safety record, complaints must be investigated to determine if safety can be enhanced further. As with all toxicological phenomena, the effects of exposure to OPs are related to dose. The present evidence indicates a low risk of OPIDN syndrome from exposure to chlorpyrifos.

Can the already low risk of chlorpyrifos use be reduced by homeowners? Here are some suggestions for ‘management’ based on the aphorism that an ounce of prevention is worth a pound of cure. First, when an insect pest problem is suspected, homeowners should seek information about the pest to help decide whether the pest needs to be controlled. Second, if a commercial pest control company is used, ask questions about alternative control methods. If an insecticide will be used, ask for information such as its chemical identity and the rate of application. Third, homeowners who apply the pesticide themselves should follow all label instructions, especially application rate and placement of chemical, and wear protective clothing. Finally, exposure to children can be reduced by well-ventilating the rooms and keeping crawling toddlers off treated surfaces for several days.

REF: Article written by Allan Felsot in Agricultural and Environmental News, 109, March 1995.


Contending that a dietary supplement poses a "risk to consumers’ health," the Food and Drug Administration has warned consumers against purchasing or consuming the product, labeled as containing Ma huang (ephedrine) and kola nut.

The agency cautioned that Nature's Nutrition Formula One, sold by Alliance U.S.A., Richardson, Texas, can cause "severe injury or death in some people." FDA said it has received more than l00 reports of injuries and adverse reactions, ranging from irregular heartbeat, heart attack, stroke, seizures, hepatitis and psychosis, to "relatively minor" conditions such as dizziness, headache and gastrointestinal distress. There have also been "several deaths" attributed to use of the product, the agency reported.

The products pose a threat due to the combination of Ma huang, a source of ephedrine, and kola nut, a source of caffeine, which can cause "severe injury," according to agency and non-agency medical experts. FDA said it informed Alliance about the supplement’s "potential health hazard" in November 1994. After receiving an "inadequate response," the agency ultimately urged the firm to recall the product.

Alliance failed to recall the supplement, FDA said, adding that this failure prompted the warning to consumers. While the company has advised the agency that it has "reformulated" the product to remove the kola nut, FDA said it is continuing to evaluate the safety of ephedrine-containing products either produced or distributed by Alliance.

REF: Food Chemical News, 37(2), March 6, 1995.


Recent advances in medicine have created a diverse and growing group of immunocompromised people who will play a bigger role in future foodborne disease outbreaks in coming decades than they do now, physician Mitch Cohen, director of the Division of Bacteria and Mycotic Disease, Centers for Disease Control and Prevention, told the ABC Research Technical Seminar last week. Immunocompromised people currently make up 25% of the U.S. population, speaker Joan Rose, University of Florida, told the group.

A growing subpopulation of immunocompromised people is going to be a major problem for food producers, manufacturers and retailers, Cohen said, because this group is far more susceptible to very low levels of any foodborne bacterium or virus and the immunocompromised are likely to suffer with more severe symptoms longer than other consumers and are more likely to die from contracting such a disease.

Along with people who have HIV or AIDS, liver disease, or have suffered illnesses affecting major organs (such as hepatitis) and recovered, the growing ranks of the immuno-compromised who are living longer because of new medicines and treatments include diabetics, organ transplant recipients (fewer than 4,000 existed in 1982; in 1992, there were 20,000) and cancer survivors (50% live longer than they did five years ago; their systems are permanently weakened by radiation, chemotherapy, other cancer treatments), according to CDC figures, Cohen said.

The elderly comprise another group that is growing in size and is immunocompromised, he noted, not because of any specific health conditions but because the human immune system weakens naturally as we age.

Future foodborne illness outbreaks are likely to involve bacteria being targeted today, Cohen said, pointing to Salmonella, Listeria, Campylobacter, Escherichia 0157:H7 and the Vibrio cholerae 01 and 0139 strains. Salmonella now is the cause of more than 50% of all foodborne illnesses per year in the United States, Cohen said.

'Breakdown of Public Health Measures' Has Had Effect

A "breakdown of public health measures" also has contributed to the rise in infectious, foodborne diseases worldwide, Cohen noted, and in the U.S. is due to: a complacency toward infectious disease (partly due to an overconfidence in medical and health-related technology), inadequate sanitation and hygiene (in homes and in food-production, food-preparation and food-serving businesses), limited resources and competing priorities for public health and medical professionals, and natural disasters.

While the potential for such outbreaks has increased, health workers have been diverted to other arenas such as AIDS work, away from identifying, analyzing and reporting on foodborne illnesses, Cohen said. In addition to health workers being diverted away from foodborne outbreaks, many such incidents go unreported by the people who fall ill and the health professionals they may contact, he said.

CDC figures showed that the outbreak associated with Salmonella in Schwan’s ice cream products last fall did not result in any deaths, but caused 102 hospitalizations, and up to 100,000 people in more than 25 states fell ill, Cohen noted, adding that laboratory tests showed the infectious dose to be very low.

"There are probably outbreaks like this that go on all the time and we never hear about it," he said, noting that a multistate, December 1992-January 1993 E. coli 0157:H7 outbreak was not identified and/or "caught" until later because physicians weren’t required to report on E. coli-caused illness at the time, and therefore didn’t do so. Also, the labs checking samples in that outbreak did not specifically check for E. coli 0157:H7 because they were not instructed to, either, Cohen noted.

Food Technology, Immigration Patterns Are Illness Factors

In addition to the increase in immunocompromised people and other predictable causes of foodborne illnesses such as high-risk activities [alcoholics eating raw shellfish, for example], there are unpredictable cases of foodborne disease that are the result of "unanticipated associations [of people and food products and habits]" and emerging pathogens, Cohen said.

An example of an unpredictable association is immigration patterns and refugee movements that may lead to people preparing a food in their traditional way, using new food sources. Cohen cited the case of a number of new Southeast Asian immigrants to Iowa falling ill from trichinosis after eating lightly cooked U.S. pork that was prepared their normal way from back home. The new immigrants did not have to worry about trichinosis in their country, where the disease does not exist, Cohen said.

Ironically, advances in food technology, just as in medicine, can lead to unexpected foodborne illness outbreaks, Cohen noted. The increase in chilled, ready-to-eat foods meant to be stored under refrigeration at the wholesale, retail and home levels has led to illness in several cases when consumers neglected to refrigerate the items, then ate them much later, he said, citing cases of botulism in California last year that were traced to supposed-to-be-refrigerated products left out on kitchen shelves for up to three weeks before being tasted/eaten .

REF: Food Chemical News, 37(1), February 27, 1995.


Lead and cadmium were detected in many seafood samples analyzed by the Food and Drug Administration in a recent survey, but none approached a level of concern, according to FDA staff.

The study consisted of 203 domestic samples and 91 import samples. Seventeen FDA field offices collected samples, which were analyzed in 10 FDA laboratories. The domestic species targeted were fresh/canned tuna, cod, pollack, catfish, salmon, flounder, Gulf Coast shrimp, blue crab, snow crab, lobster, white fish and perch. For import analysis, targeted species were shrimp (wild and aquaculture), canned tuna, cod and salmon.

Results were reported by product, as follows: Blue crab: lead levels, ranging from 0 to 364 parts per billion, cadmium levels ranging from 0 to 630 ppb; canned tuna: 0-650 ppb lead, 0-40 ppb cadmium; catfish: 0-816 ppb lead, 0-43 ppb cadmium; cod: 0-600 ppb lead, 0-88 ppb cadmium; flounder: 0-20 ppb lead, 0-16 ppb cadmium; lobster: 0-28 ppb lead, 9.9-820 ppb cadmium; perch: 0-25 ppb lead, 2.4-9.8 ppb cadmium; pollack: 0-49 ppb lead, 0-16 ppb cadmium; salmon: 0-209 ppb lead, 0-16 ppb cadmium; shrimp: 0-92.5 ppb lead, 0-203 ppb cadmium; snow crab: no lead, 0-78 ppb cadmium; fresh tuna: no lead or cadmium.

REF: Food Chemical News, 37(1), February 27, 1995.

Assessment of the Impact of a 100% Smoke-Free Ordinance on Restaurant Sales -- West Lake Hills, Texas, 1992-1994

Exposure to environmental tobacco smoke (ETS), which is associated with adverse health effects among nonsmokers, is a health hazard of particular concern for patrons and employees in restaurants. To protect nonsmokers, many local governments have enacted ordinances requiring restaurants to be smoke-free. However, the potential economic impact of these laws on restaurants is an important concern for restaurant owners. On June 1, 1993, the city of West Lake Hills (a suburb of Austin), Texas (1995 population: 3000), implemented an ordinance requiring a 100% smoke-free environment in all commercial establishments to which the public has access, including all restaurants and restaurants with bar areas. This report summarizes an assessment of sales in restaurants during June 1993-December 1994 compared with January 1992-May 1993.

Editorial Note: The findings in this report are consistent with assessments using similar methods in other locations that have reported that the implementation of smoke-free ordinances has not been associated with adverse economic effects on restaurants.

Previous reports of decreases in restaurant sales following the enactment of clean indoor air ordinances have been based on anecdotal information, on studies that used restaurant owners' self-reports of the impact on their business instead of validated sales data, and on studies that used tax data to measure restaurant sales but collected data for only one or two quarters following implementation of ordinances. In comparison, the assessment in West Lake Hills was based on sales data that were validated by tax revenue reported by the State Comptroller's office, included data for periods of time sufficient for statistical analysis, and employed multiple linear regression techniques to account for temporal trends and seasonal variations in sales.

The findings in t0his assessment are subject to at least three limitations. First, because of limitations in data, an ordinary least squares regression model -- which assumes no autocorrelation -- was used in place of a more specific time series model; however, the Durbin-Watson statistic indicated that significant autocorrelation was not present. Second, the model only explained 33% of the variation in total restaurant sales; future studies may benefit from the inclusion of other variables that can affect restaurant sales. Third, because the assessment focused on a consistent panel of restaurants and excluded restaurants that opened during the assessment period, the findings cannot be generalized to all restaurants in West Lake Hills.

The economic impact of smoke-free ordinances is an important consideration for policymakers concerned about the ETS exposure of nonsmokers; assessment of the potential economic impact of these laws should be based on the most objective, scientific evidence available. The findings from the assessment in West Lake Hills has provided policymakers in that community with a scientific appraisal of the impact of public health measures to reduce exposure to tobacco smoke. In addition, the assessment in West Lake Hills provides a model for other local and state public agencies to consider when evaluating tobacco-control programs.

REF: Morbidity and Mortality Weekly Report, 44(19), May 19, 1995.


World No-Tobacco Day, 1995

The increase in cigarette smoking worldwide since 1950 has been particularly dramatic in developing countries and has been associated with substantial morbidity, mortality, and economic costs. Each year, tobacco use accounts for at least 3 million deaths worldwide. Based on current smoking trends, in 30-40 years, tobacco use is projected to cause 10 million deaths annually, of which 70% will occur among persons in developing countries. The global health-care costs resulting from tobacco use exceed $200 billion per year -- more than twice the current health budgets of all developing countries combined.

REF: Morbidity and Mortality Weekly Report, 44(19), May 19, 1995.

Illegal Application Results in Prison Term

In Minnesota, a pesticide applicator who illegally applied chlorpyrifos (Dursban) to oats has been sentenced to five years in prison. In November, he was convicted of mail fraud, food adulteration and misuse of pesticides. He also must perform 200 hours of community service lecturing on the hazards of pesticides. The contaminated oats were owned by General Mills and resulted in $150 million in damaged cereal (160 million boxes). Dursban is not registered for use on oats; chlorpyrifos-methyl (Reldan) is registered but is more expensive.

REF: Agrichemical and Environmental News, 109, March 1995.

E.coli 0157:H7 Outbreak

We received the following information via Internet from the USDA Extension Service.

The latest E. coli outbreak occurred in Missoula County, Montana. As of July 24, 1995, 63 people were identified with bloody diarrhea, etc, and 23 people had been found to be positive for E. coli 0157:H7 on culture. Although first thought to be due to undercooked meat at a fast food restaurant, attention is now focused on lettuce raised locally. Apparently an organic farming enterprise using cow manure for fertilizer and irrigating with water from a pond that gets surface runoff water. In this case some of the runoff comes from a nearby cattle facility. Although not yet finally confirmed, all indications are now that it was not the meat, but the lettuce which was the source.

" Frequently Asked Questions (FAQs) "

Oleander Used in Compost

We receive many calls asking about the toxicity of oleander and the use of compost which contains oleander. Oleander contains cardioactive glycosides which are sugars linked to steroid-like molecules, one of which is called oleandrin. These chemicals affect the conductivity and contractility of the heart, and at toxic doses, causes heart failure. Similar chemicals from purple foxglove (digitalis glycosides) are used at low doses to treat heart failure, but at high doses exhibit similar toxicity.

In cooperation with Advisor Jim Downer and Veterinary Diagnostic Toxicologist Frank Galey, we have looked at the fate of oleandrin in composted oleander. We suspected that it would break down during composting, and that a similar breakdown would occur in oleander leaves which get into the soil. Preliminary results show that the composting process does indeed result in a substantial reduction of oleandrin in leaves.

Can oleander compost be used safely in vegetable gardens?

The size, complexity, and instability of the glycosides make it highly unlikely that they will be transported into crops. I know of no studies showing such transport, and I know of none showing that it does not occur. I would use compost containing oleander in my own vegetable garden without worry. Just don’t eat the compost.

Is the smoke from burning oleander a hazard?

We have tried to find some definitive data on this in the literature, and can find nothing. If anyone has anything more than anecdotal reports, please let us know. Because of the known toxicity of these chemicals, and the possibility that they might be attached to smoke particulates and be inhaled, discretion dictates a recommendation to avoid smoke from burning oleander until better information is available.

Art Craigmill


Update on Clenbuterol

For several years, FDA has been concerned about the use of clenbuterol, a drug not approved for veterinary use in the U.S., to increase muscle in meat-producing animals, particularly show animals. FDA is concerned about this practice because of possible adverse health effects in people who might consume food from treated animals. FDA’s concern is based on the fact that clenbuterol is a beta-agonist drug. Beta-agonist drugs affect lung and heart function, and illegal use can present a hazard to consumer health.

FDA, several State agencies, and private organizations such as State fairs have received information concerning the use of clenbuterol in show animals such as cattle, pigs, and sheep. The drug has been used to increase muscle and decrease fat deposition. Some exhibitors believe this effect will help their animals to win.

Clenbuterol is approved in Canada, many European and South American countries, Australia, and New Zealand for use in nonfood-producing animals. A few countries have approved it for therapeutic uses in food-producing animals. The levels needed to achieve therapeutic effect are much less than those required to increase muscle mass.

FDA’s main concern about the use of clenbuterol is its possible adverse effect of residues on public health. In 1990, there were reports from Spain of illness in 135 individuals (including some who were hospitalized) who consumed beef liver from treated animals. These illnesses were traced to illegal residues of clenbuterol in the liver which these individuals consumed. These individuals exhibited symptoms such as increased heart rates, muscle tremors, headache, dizziness, nausea, fever, and chills. In 1991, there was a similar outbreak of food poisoning reported from France involving 22 people who consumed beef liver with clenbuterol residues.

While the residue-produced clenbuterol toxic effects have been described as mild, FDA considers all unintended effects to be unacceptable. Also, it is possible that individuals being treated with adrenergic agents, or otherwise sensitive to these drugs, may be far more severely effected by toxic levels of clenbuterol than are normal, healthy individuals.

FDA is also concerned about the illicit use of clenbuterol leading to occupational-related illness or death. It is possible that clenbuterol effects on the cardiovascular system may be more hazardous via occupational inhalation exposure than via ingestion in food. However, the Agency has not been able to confirm reports of such reactions.

FDA continues to receive reports of the use of clenbuterol in show animals. In 1994, traces of clenbuterol residues were found in animals at stock shows held in Ohio and Oklahoma. At the Oklahoma State Fair in Tulsa, a clenbuterol test of champion animals disqualified six animals including steers, sheep, and a hog. At the National Western Stock Show held in Denver in 1995, the Grand Champion steer and Reserve Grand Champion steer were later disqualified because of findings of clenbuterol residues. The exhibitors of those animals agreed to be disqualified and to accept full responsibility for the presence of clenbuterol in their animals.

Clenbuterol begins to appear in urine and body organs within a day of administration and can remain in the liver for several weeks. But, the body also begins to eliminate the drug from the body immediately. Thus, it is possible for low levels of the drug to go undetected in urine and edible tissue if sufficient time has passed before slaughter. However, the exposure of animals to clenbuterol can be monitored by assaying the retinal tissue from the eyes of animals. Unlike urine and liver, retinal tissue retains clenbuterol for long periods of time.

In September 1994, FDA began using a new test which could detect these residues in the retina, where clenbuterol residues can reside for at least five months. It was this new test which lead to detection of the residues in show animals in Ohio, Oklahoma, and Colorado.

FDA is working with State departments of agriculture and other organizations to encourage testing of animals from livestock shows for the presence of clenbuterol and to eliminate the use of this drug. Groups such as the National FFA Organization (Future Farmers of America) and the National Cattlemen’s Association are also working to end the use of this drug in food-producing animals. In an interview with the FDA Veterinarian, Dr. Larry D. Case, National Advisor and Chief Executive Officer of the National FFA Organization, stated "I am appalled about the use of clenbuterol in food animals." He believes that the use of clenbuterol and other illegal drugs is extremely serious because these animals become part of the human food supply. He pointed out that the National FFA Organization does not condone the use of illegal drugs in any manner. The National FFA Organization is working with State and local chapters to help prevent this problem.

Dr. Gary L. Cowman, Director of Beef Quality Assurance of the National Cattlemen’s Association, has stated "Our industry does not condone illegal drug use . . . ." "The beef industry, through the efforts of its Beef Quality Assurance program has worked very hard . . . to assure that beef is produced free of any violative residues. It is extremely unfortunate that a very small group of individuals put winning above the safety and wholesomeness of the product produced."

Based on FDA’s high level of concern for adverse effects to consumers from illegal use of clenbuterol in the U.S., the Agency intends to use all means available to stop the illegal importation, distribution, and use of this drug. FDA is pleased with the effectiveness of our partnership with State Fair organizations and State officials to help detect and eliminate the illegal use of clenbuterol.

REF: FDA Veterinarian, May/June 1995.


A lot of press has been given to the drug clenbuterol in the last year. What is this drug and what is the issue? What can you tell your clients about the ramifications of the use of this drug?

The Drug—Clenbuterol is a beta-2-adrenoceptor agonist. Its primary action is in relaxing smooth muscle; e.g. uterine, bronchial. It also has anabolic effects and has been named a "repartitioning" agent. It can mobilize energy substrates by increasing fat breakdown (lipolysis) and can down-regulate lipogenesis while promoting muscle growth.

The Issue—Some producers of veal, beef, and lamb, and owners of show lambs and cattle (including 4-H) have used this drug to improve gain and muscling of their animals, like an anabolic steroid. The dose to induce the anabolic effects is 5 to 10 times higher than doses used for therapy of bronchial diseases. The drug is illegal in the US; and if meat is tainted with its residues, people eating this meat can develop immediate and severe flu-like reactions, sometimes requiring hospitalization.

In Spain, 135 people were hospitalized within 1/2 to 6 hours after eating liver tainted with clenbuterol. They developed cardiac arythmias, accelerated heart rates, and muscle tremors in addition to flu-like symptoms. In 1991, 22 people in France were poisoned by clenbuterol-contaminated veal liver. They had symptoms including tremor, headache, tachycardia, dizziness, and palpitations. In a few people, muscle pains developed. The signs occurred 1 to 3 hours after consuming the liver and resolved within 2 to 3 days. The use of this drug is apparently widespread in the veal industry in Europe, although illegal in most countries for use in food animals.

Last year in Ohio, use of clenbuterol in fair animals was discovered. At the Tulsa State Fair in Oklahoma, 6/38 animals tested were positive for clenbuterol. The grand champion and reserve champion steers at the Denver show were also positive. Recently, the drug has been smuggled into the US from the Netherlands for use in veal and lambs. Anecdotal information leads us to believe that the use is fairly widespread throughout the US, particularly for show animals.

This issue is not a new one, the USDA/FSIS announced in 1991 that meat which tests positive for clenbuterol would be condemned. FDA is already alerting customs officials about illegal importation and was taking steps to investigate the distribution, sale, and use of the drug. Why is this illegal drug still an issue? Prizes for winners at shows as well as commercial uses and lack of largescale testing may have led to more widespread use.

Use in Veterinary Medicine—Clenbuterol is not approved for any use in the US and is not approved for use in cattle in Canada. In Europe, the drug has been used as a bronchodilator in horses and in cases of chronic obstructive pulmonary disease. In 1989, it was legal to use it in veal calves in the Netherlands for a maximum of 14 days for "clinical indications of respiratory disease." At certain dosages, it can increase muscle mass and decrease fat deposition and has been given orally for this purpose. The economics of the grading system in the European Union rewards lean carcasses and provides an incentive to use clenbuterol illegally.

Clenbuterol’s smooth muscle relaxant effect has been used as an aid in bovine dystocias (difficult labor) when manual correction was necessary by reducing myometrial activity. It has also been used in cases of equine uterine torsions. An experiment in Japan showed that the drug was effective at eliminating night-time calving and lowering incidences of dystocia and retained placentae in treated cows.

There may be some negative effects on animals treated with clenbuterol. If fed to increase muscle mass, it can actually have a negative influence on body growth and feed efficiency if the animals are fed low protein diets. Side effects such as tachycardia, vasodilation, and muscle tremor have been seen in calves after an anabolic dose was given. When fed to cattle over a period of two days, the drug caused the heart rate to increase by 92 to 117 percent. When fed to veal calves in milk replacer, use was associated with higher liver condemnations due to abscesses and hepatitis.

In an experiment with gilts fed 1 ppm clenbuterol for 40 days, the treated animals developed cystic ovaries, had uterine atrophy, and a reduction in progesterone concentrations. This suggested a change in the hormonal activity of treated animals. When given to sexually vigorous male rats, clenbuterol reduced sexual activity; but when given to sexually sluggish rats, it resulted in increased activity.

Use in Human Medicine—Beta 2-adrenoceptor agonists, like clenbuterol, have use in human medicine as bronchodilators, to relax bronchial smooth muscle and for treatment of bronchial spasm. It may also suppress the release of leukotrienes and histamine from lung mast cells and may enhance mucociliary function. Clenbuterol has been used in human patients with chronic productive cough, asthma, and chronic obstructive pulmonary disease. It can be administered subcutaneously, via inhalation, or orally and is readily absorbed.

Current research is focussed on its use, and the use of a similar drug—salbutamol (albuterol), to reduce or restore skeletal muscle losses in catabolic states, such as during clinical hyperthyroidism. There may even be a potential use in certain orthopedic conditions where muscle-wasting is an issue.

Clenbuterol is abused not only by some animal owners but also by some athletes. Some bodybuilders use this drug to increase muscle mass; and if abused, the individuals may present to a physician with heart palpitations. Adverse side effects may occur even with therapeutic doses and include contact dermatitis, restlessness, skeletal muscle tremors, apprehension, anxiety, and tachycardia. Large doses given to lab animals have resulted in myocardial necrosis.

FDA/USDA Response—The FDA has declared that use of clenbuterol is illegal in the US and has set a zero tolerance. The FDA is very concerned about the use of this drug and is currently working on cases for prosecution.

Testing for clenbuterol has relied on detecting residues from body fluids or tissues. Depending on the dose, residues in the liver have been detected up to 56 days after the last feeding of clenbuterol. Analysis of retinal extracts extends the detection time beyond the time it can be detected in liver, urine or bile. This sample source is currently approved and advocated by the FDA. Analyses include ELISA and gas chromatography/mass spectrometry.

The Bottom Line—Clenbuterol is illegal and poses a significant health risk to the consuming public. Show officials and judges, animal owners and producers should be made aware of this issue. Veterinarians can make their clients aware and help them avoid contaminating the food supply and risking prosecution.

At the Pennsylvania Farm Show next year, the first four places for each species will be tested for clenbuterol, furosemide, acepromazine, and perhaps phenylbutazone. The Pennsylvania Department of Agriculture will be doing the testing.

REF: Dr. Dale Moore, Herd Health Memo, (Penn State Univ) May 1995.


The Food and Drug Administration’s Center for Veterinary Medicine will continue to crack down on clenbuterol use in livestock shows, a top CVM official told Food Chemical News. FDA field staff and state officials have already discovered cheaters at the Tulsa, Denver and Louisville livestock shows.

Clenbuterol is a beta-agonist that helps turn food consumed into muscle instead of fat, the CVM-er explained. It is not truly a "steroid" as has been reported in the press, the staffer added.

CVM is particularly concerned about the use of this illegal drug because it has caused human illness in Europe, particularly in Spain in 1990, where 135 people were hospitalized after eating clenbuterol-tainted meat (the drug was recovered from their urine). Clenbuterol tends to accumulate in the liver, which was what most victims had consumed.

"We were determined to avoid a crisis like that," explained the CVM-er, and in 1991 CVM and the U.S. Agriculture Department sent out a letter to state departments of agriculture warning them of clenbuterol use, especially in the show circuit.

FDA could do little more at the time, however, since there was no test for clenbuterol reliable enough to stand up in court. But Dutch scientists working on the problem discovered that the drug tends to remain in pigmented tissues. Using this information, they were able to develop a reliable clenbuterol test using cattle retinas.

"In early 1994, we received a call again from state fair officials in Oklahoma," explained the CVM staffer. The officials were so concerned that they held a public meeting for professional exhibitors on the issue. The exhibitors told the state officials that they used the drug "and we know that you don’t have a test that is good enough" to stand up in court, the staffer said.

Use in State Fair Animals Spurred Government Researchers to Validate Method

This spurred the federal government to get together a group of 30 analytical scientists from many different government agencies to work together to validate the clenbuterol method in time for the state fair in Tulsa. They succeeded in validating the method in September, in time for the show, the staffer said.

CVM has since found clenbuterol use in two other major livestock shows. The center will continue to examine livestock at shows for use of the drug, the CVM-er said. The livestock press has come down hard against the use of clenbuterol, since the major purpose of most of these shows is to teach youngsters how to raise quality livestock.

Most recently, the two top steers in the National Western Stock Show held Jan. 10 in Denver were found to contain clenbuterol. Randy Rash, the 16-year-old who won for grand champion steer, named Badger, and his parents, John Ben Carrabba and Cherie Carrabba, admitted to clenbuterol use. In addition, the reserve grand champion, named Wyatt, exhibited by 18-year-old Amy Brackney, also was found tainted by the drug. Mike Brackney, the girl’s father, admitted to knowledge of the use of clenbuterol in the animal.

After hearings by the Western Stock Show Association, the two steers were disqualified and the two families barred from exhibiting any animal at any future National Western Stock show.

The Carrabbas and the Brackneys agreed to give up all prize money and money paid for the animals by cattle farmers. They also agreed to pay for charges involved in the investigation. The three parents, after initially denying the charges, agreed to release a statement, parts of which follow:

"We wish to apologize for the damage that this incident has caused to the National Western Stock Show and to junior livestock competitions everywhere..... This painful incident should underscore the importance that all parents and exhibitors accept the consequences of any rules violations, regardless of whether they are technical, practical, willful, intentional, accidental or negligent. Only in this way can all junior exhibitors compete on a fair and even basis."

REF: Food Chemical News, 37(5), March 27, 1995.


Heavy mouse infestations were found to significantly increase the likelihood that a hen house was environmentally positive for Salmonella enteritidis, according to a three-year pilot study that surveyed more than 130 flocks and hundreds of thousands of eggs.

REF: Food Chemical News, 37(15), June 5, 1995.

Toxin in Pine Needles Identified

The mysterious poison in pine needles that causes pregnant cows to abort or deliver weak, premature calves has been identified by U.S. Department of Agriculture scientists as isocupressic acid. USDA scientists hope identifying the yellow, oily substance in the ponderosa pine needles will lead to finding an antidote, or other ways to protect pregnant cows.

Based on initial studies, USDA scientists have identified a daily isocupressic acid dose that is likely to induce labor within 2 to 8 days. That dose, about 200 milligrams per kilogram of the cow’s weight, is a little less than a quarter cup of toxin a day.

Kip Panter, USDA reproductive toxicologist, says the average 1,200 pound cow could easily eat enough pine needles in a day to ingest that much of the toxic acid. He says the researchers now plan to look at environmental factors, such as temperature, that might cause the amount of toxin in the needles to vary.

REF: Florida Veterinary Scene Newsletter, 4(5), May/June 1995.

Toxicity of Melaleuca Oil and Related Essential Oils Applied Topically on Dogs and Cats

Melaleuca oil is marketed for use on dogs, cats, ferrets, and horses in skin-care products for cleaning, healing and relieving itching associated with allergies, insect bites, hotspots, abrasions and other minor rashes and irritations. It also makes claims as a deodorizer, detangler and external parasite repellent. It has proven antibacterial and fungicidal properties. Melaleuca oil is obtained by steam distillation of the freshly harvested leaves of the Melaleuca alternifolia tree, also known as the Australian Tea-tree. Oil of Melaleuca is colorless or pale yellow, and active ingredients are predominantly cyclic terpenes. Toxicology of this oil is similar to that associated with oil of turpentine, which is rapidly absorbed by dermal and oral routes.

Cases of Melaleuca oil toxicosis have been reported by veterinarians to the National Animal Poison control Center when the oil was applied dermally to dogs and cats. In most cases, the oil was used to treat dermatologic conditions at inappropriate high doses.

Typical signs observed in dogs and cats include ataxia, incoordination, weakness, tremors, behavioral disorders, and depression. Onset of clinical signs after topical application of different products containing Melaleuca oil usually occurs 2 to 8 hours later. Removal of residual amounts of oil from the skin by a bath in non-insecticidal shampoo is recommended. Intravenous fluids and glucose may also strengthen the animal.

In cases of oral ingestion, which might result from grooming activity in cats, activated charcoal and a cathartic is recommended in order to decrease absorption from the intestinal tract. Treatment of clinical signs and supportive care is usually sufficient to achieve recovery without sequelae within 2 to 3 days.

REF: Florida Veterinary Scene Newsletter, 4(5), May/June 1995.


Fewer than 4,000 milk samples tested positive for animal drug residues in more than 4 million samples reported to the National Milk Drug Residue Data Base, according to a report on the data base covering the period Oct. 1, 1993 to Sept. 30, 1994.

Of the 4,179,108 samples covered by the report, 3,693 were positive for a residue. A total of 4,589,085 tests were reported on the samples covering 14 different groups of drugs or individual drugs. Forty separate testing methods were used to analyze the samples for residues.

The report, dated March 31 and prepared for the Food and Drug Administration by GLH, Inc. of Falls Church, Va., defines a sample as "representing a load or lot of milk sampled and analyzed, e.g., a bulk milk pickup tanker, producer, or over-the-road tanker, a silo, etc."

A "positive" in the report "means that the sample was found to be positive for a drug residue by a test acceptable for taking regulatory action in a certified laboratory by a certified analyst, or the milk was rejected on the basis of an initial test by the milk processors."

The samples included 3,926,521 conducted by industry, which yielded 3,248 positives, and 252,587 conducted by regulators, predominantly at the state level, which yielded 445 positives.

The report noted that 68,076,000 pounds of milk which tested positive were disposed of in accordance with pasteurized milk ordinances.

The data base includes 3,213,220 samples from bulk milk pickup tankers, 61,775 from pasteurized fluid milk and milk products, and 824,132 producer samples, as well as 79,981 samples from other sources. It includes samples of both Grade A and Non-Grade A milk, with roughly of the samples being Grade A.

The most common positive result indicated in the report is for beta-lactams, which was also by far the most common test done. There are some 4,310,118 tests for beta-lactams included in the data base, some 7,256 of which were positive.

The report does not specify the number of positive tests that were violative because many of the tests conducted were screening tests rather than tests that could determine precise levels of the drugs found, according to Joe Smucker in the Milk Safety Branch of FDA’s Center for Food Safety and Applied Nutrition. Violative samples are reported in the National Drug Residue Milk Monitoring Program, which involves far fewer samples.

REF: Food Chemical News, 37(10), May 1, 1995.

FDA Analyzes Pesticides in Animal Feeds

In Fiscal Year 1994, 589 domestic feed samples (537 surveillance and 52 compliance) and 63 import feed samples (all surveillance) were collected and analyzed for pesticides by the FDA. Of the 537 domestic surveillance samples, 240 (44.7 percent) contained no detectable pesticide residues and 7 (1.3 percent) contained residues which exceeded regulatory guidance (see table below). Of the 63 import surveillance samples, 29 (46.0 percent) contained no detectable pesticide residues, and none contained residues which exceeded regulatory guidance. The 7 domestic surveillance samples which exceeded regulatory guidance involved 2 commodities with residues which exceeded a tolerance and 5 commodities with residues for which no tolerance had been established.

In the 297 domestic surveillance samples in which one or more pesticides were detected, malathion, chlorpyrifos-methyl, diazinon, and chlorpyrifos were the most frequently found and accounted for 83.2 percent of all pesticide residues detected in feed. The range and median of these four pesticides are shown in the table below.

Pesticide Number of Samples Range Median
malathion 217 trace - 49.000 ppm .060 ppm
chlorpyrifos-methyl 91 trace - 1.500 ppm .048 ppm
diazinon 54 trace - .228 ppm .016 ppm
chlorpyrifos 33 trace - .025 ppm trace

Summary of the domestic feed samples collected and analyzed by the FDA in Fiscal Year 1994 for pesticide surveillance.

TYPE OF FEED Number of
Samples with No
Pesticide Residues
Samples Exceeding
Regulatory Guidance
Whole/Ground Grains 204 109 (53.4%) 3 (1.5%)
Mixed Feed Rations 131 25 (19.1%) 0 (0.0%)
Plant By-products 81 30 (37.0%) 1 (1.2%)
Animal By-products 76 44 (57.1%) 0 (0.0%)
Hay & Hay Products 40 31 (77.5%) 3 (7.5%)
Minerals/Supplements 5 1 (20.0%) 0 (0.0%)
TOTALS 537 240 (44.7%) 7 (1.3%)

REF: FDA Veterinarian, X(II), March/April 1995.


Dairy farmers are proceeding with varying degrees of caution in their use of recombinant bovine somatotropin, according to research on rBST use in Wisconsin, California, and Ontario County, New York, presented Feb. 18 at the annual meeting of the American Association for the Advancement of Science in Atlanta.

There is limited use in Wisconsin, where farmers’ resistance to the synthetic hormone has hardened, reported Bradford Barham, an agricultural economist with the Agricultural Technology and Family Farm Institute (ATFFI) at the University of Wisconsin-Madison.

About 20% of California dairy producers are using rBST, according to research reported by L.J. (Bees) Butler of the Department of Agricultural Economics at the University of California-Davis.

Loren Tauer, professor of agricultural resources and managerial economics at Cornell University, indicated some 39% of the farmers in Ontario County were using rBST in 1994, and projections are that rBST use could reach 50% this year.

Five and one-half percent of Wisconsin dairy farmers were using rBST in their herds, according to a fall 1994 ATFFI survey, Barham said. He further indicated that 90% say they are unlikely to or will never use rBST. The 5.5% figure is an increase from the 1.9% of farmers who said in a spring 1994 survey that they were using the hormone. During the same time the number of farmers indicating they are unlikely to use rBST or would not use it under any circumstances rose from 85.7% to 90.1%.

The Wisconsin results were based on a mail survey of about 1,050 Wisconsin farmers with nearly a 60% response rate.

Barham cautioned that if rBST use in Wisconsin falls much below use in other states, farmers in Wisconsin could become less competitive. He pointed out that one factor influencing the level of rBST use could be the fact that almost all milk haulers in the state guarantee that their milk comes from cows not treated with rBST, even though only 6% of Wisconsin’s milk is consumed as fluid milk. Most Wisconsin milk is made into cheese, Barham said and prices in that market are lower and highly competitive.

In May 1994, Wisconsin approved a voluntary labeling law for milk from rBST-treated Cows.

Only 8.5% of California Herd Treated

In addition to the 20% of California farmers who reported use of rBST, another 23% expressed interest in using it in the future, Butler reported. He indicated that only about 8.5% of the total California dairy herd is being treated with rBST, however, because farmers do not treat all their cows.

California milk production rose 9% in 1994, Butler said, with the impact of rBST accounting for only about 1%. Butler said California dairy farmers are reluctant to disclose to other farmers whether they are using rBST.

Knowledge of Research Could Roster rBST Use in New York

Tauer suggested that the high adoption rate in Ontario County could result from the fact that much of the basic research on rBST was done in New York and farmers were kept apprised of developments through Cornell Cooperative Extension.

The Ontario County results were based on interviews of up to four hours with 50 farmers. Originally the survey found that almost 50% of farmers were using rBST, but the study found a dropout rate of 25% after one year. The study also found that five dairy farmers plan to use the hormone in the next year, which will return the use rate to 50%.

Other findings of the Cornell research included:

- generally the farmers using rBST gave it to only 25 to 50% of their herd;

- farmers generally did not treat low-producing cows and in many cases resisted giving the hormone to their high-producing cows;

- milk yield increases averaged 15%;

- cows treated with rBST generally consumed 5%-10% more forage and grain;

- farmers indicated that increased labor costs were a major disadvantage of using the hormone;

- five of the farmers surveyed indicated that some of their herd might have experienced rBST-related health problems ranging from foot problems and mastitis to breeding difficulties and thinness. "In all fairness, some of these health problems could have occurred even without the use of rBST, but respondents associated them with the use of the hormone," the Cornell researcher said.

Characteristics of rBST-Using Farmers Similar

All three researchers found similar characteristics among the farmers who are using rBST. Compared with farmers who do not use rBST, farmers using the technology are younger, have more formal education, manage larger herds of cows with higher per-cow production, and use other technologies, such as total mixed rations, that increase milk production, Barham reported.

Butler said, "As might be expected, current and future users tend to have larger herds, higher average herd productivity and slightly lower cost of production than non-users. In addition, most current and future users plan to increase production in the next few years, and also tend to be users of computers and other technologies more than the average non-user."

The Cornell research found that those who use rBST tend to run larger facilities and view their work more as a business as opposed to a way of life. The research also indicated that rBST users were already using advanced dairy technologies, like artificial insemination and personal computers.

REF: Food Chemical News, 37(1), February 27, 1995.

Art Craigmill
Extension Toxicologist
U.C. Davis