COOPERATIVE EXTENSION UNIVERSITY OF CALIFORNIA
ENVIRONMENTAL TOXICOLOGY NEWSLETTER

Vol. 8 No. 1 June 1988

Pesticide Residues in Foods

Table of Contents

I. Pesticide Residues in Foods
II. International Toxicology News
III. Organophosphate Toxicity

PESTICIDE RESIDUES IN FOODS
Carl Winter

A recent consumer attitude survey by the Food Marketing Institute indicated that consumers are more concerned about the potential health effects of pesticides in their food supply than from any other food safety issues, including cholesterol, antibiotics, food additives, or irradiation. Seventy-six percent of those surveyed indicated that pesticides were a major area of concern. About the same time the results from the consumer survey appeared, the National Academy of Sciences (NAS) published a book "Regulating Pesticides in Food: The Delaney Paradox " which summarized Federal regulations pertaining to pesticide residues in fresh produce and processed foods, pointed out inconsistencies in the regulatory process, and made estimates of otential human risks posed by pesticide residues. Under worst-case assumptions, it was reported that approximately 1.46 million cases of cancer in the United States could occur from residues of only 28 pesticides in our food supply. Findings from both the consumer survey and the NAS report indicate that the subject of pesticide residues in foods is a matter of supreme importance, and have led several groups to call for major changes in the regulatory programs.

On the other side of the coin, the United States Food and Drug Administration (FDA) considers pesticide residues in foods as only their fifth priority in terms of food safety issues. Far more important, in the eyes of the FDA, are 1) microbial contamination; 2) nutritional imbalance; 3) environmental contaminants; and 4) naturally-occurring toxins. Food additives were ranked sixth, behind pesticide residues.

How can we explain these apparent inconsistencies in the perceived risks from pesticide residues in foods? Why is it that some groups are calling for immediate governmental action to overhaul the present system of regulation while others maintain a calmer "not-to-worry" attitude?

To start, it is important to understand how pesticide residues in foods are regulated. Residues are regulated by the tolerance system, with the tolerance defined as the maximum allowable level of pesticide residue on a particular crop. Individual tolerances are established for specific pesticides on specific crops and are determined by the Environmental Protection Agency (EPA). If the tolerance level for a pesticide is exceeded, the food crop will not be allowed to be sold. Additionally, if any residue of a pesticide on a crop is detected for which a tolerance is not established, the residue is also deemed illegal and the food cannot be sold.

One common misconception regarding pesticide tolerances lies in understanding the method by which they are established. It is logical to assume that tolerances would be based upon the maximum acceptable levels determined by the EPA to not significantly affect human health. In practice, however, tolerances are not set on the basis of potential health effects, but, instead, are set by the maximum levels of the pesticide which would be expected to be present following a legal application of the pesticide. In requesting a tolerance, a pesticide manufacturer performs a series of tests in a variety of geographical locations using the most severe application conditions, including the maximum legal application rate of the pesticide, maximum numbers of applications, and minimum legal preharvest intervals. Tolerances are set to be slightly higher than the maximum residue levels detected in the field tests.

Health assessments are performed by the EPA using the typical levels of the pesticide found in the field tests. For most pesticides, an Acceptable Daily Intake (ADI) has been established which is often set at 100 times lower than the lowest dose shown to cause any type of non-carcinogenic toxic effect in test animals. Since a single pesticide may be used on a variety of crops, the EPA considers exposure to the pesticide from all registered crops by making estimates of typical food consumption patterns. If the proposed tolerance of a pesticide on a new crop causes the normal total exposure levels on all crops to exceed the ADI, the pesticide will not be allowed to be used on the particular crop. Typically, however, tolerance levels are established at levels far below those necessary to exceed the ADI.

The responsibility for monitoring foods for pesticide residues and enforcement of regulations at the federal level is given to the FDA. California has developed its own program which is conducted by the California Department of Food and Agriculture (CDFA). The CDFA program primarily monitors foods produced and sold within the state. The FDA tests for residues in foods entering California from foreign countries and from other states at the border stations, although CDFA has also established a major border inspection program. In 1987, CDFA analyzed over 13,400 food samples for pesticide residues. This number is comparable to the total number of samples taken by the FDA throughout the country annually.

The actual levels of pesticide residues are highly-debated. The most comprehensive data on pesticide residue levels is that reported by CDFA. In 1987, 7,010 samples of CDFA's routine marketplace sampling were analyzed for residues using a multi-residue screening procedure capable of the detection of over 100 pesticides. In 79.8 percent of the samples, no residues were detected. This figure is particularly significant when one considers that modern instruments for chemical analysis can routinely detect chemicals in the parts per million (ppm) range and below. To gain some perspective, one part per million is equivalent to one ounce in 31 tons. Residues below 50 percent of the tolerance levels were detected in 17.7 percent of the samples, while residues between 50 and 100 percent of the tolerances were detected in only 1.0 percent of the samples. In 0.3 percent of the samples, residues were detected that were in excess of the established tolerance, while 1.2 percent of the samples contained detectable levels of pesticides that were not registered for use on the crop analyzed. Similar findings have been reported in the annual reports of the past several years.

Much of the controversy surrounding the issue of pesticide residues in foods has been derived from the public's mistrust of CDFA's data, since the CDFA results are not consistent with findings from other groups. Data from the FDA suggest that about 50 percent of foods analyzed contain no detectable residues. The National Resources Defense Council reported that 56 percent of samples had no detectable residues, while independent laboratories reported that 54 percent contained no residues.

Many of these apparent differences can be explained on the basis of the sensitivities and scopes of the various analytical techniques employed. The CDFA multi-residue program is capable of detection of only about one-third of all registered pesticides, although it has been estimated that this one-third may correspond to about 80 percent of total pesticide use in California. The CDFA multi-residue screen is also not as sensitive as some of the other methods used since it is tailored to achieve rapid results over a broad spectrum of chemicals. The FDA program monitors for over 200 different pesticides and can achieve lower detection limits than CDFA but is limited by the fact that it may take several weeks to obtain data from the analyses. Independent laboratories are often provided with information concerning what pesticides were actually applied to the crop; this allows the laboratories to focus their analyses on only a few pesticides and makes more sensitive analysis (lower detection limits) possible.

While there is controversy regarding what percentage of foods are "free" of pesticide residues, there is general agreement that the typical levels of pesticide residues in our foods are far below the levels allowed by law. Arguments as to the actual percentage of foods containing "detectable" residues are dangerous in that they cloud the public's ability to accurately understand risk calculations. The "presence-or- absence" approach incorrectly implies that any food with pesticide residue is hazardous and that only those certified to be free of pesticides are safe. This contradicts the fundamental principle of toxicology which states that the risk from exposure to a substance depends upon the dose of the substance and not just its presence. The public's difficulty in understanding this principle was pointed out in a recent study in which 45 percent of consumers reported that even the smallest amount of a potentially unsafe ingredient in their food did not reduce their fear of that ingredient.

There are three major reasons why the pesticide residue levels in foods are relatively low:

1) Pesticides are not always used on crops for which they are registered. Application of pesticides is expensive to growers; if they can manage to get by without using pesticides, they will.

2) The edible portion of the plant is not always exposed to the pesticide. In many cases, pesticide applications are made before the plants have emerged or prior to formation of edible fruits and leaves.

3) Tolerance levels are established under the most severe conditions of use. Many pesticides are used at lower application rates, with fewer applications, and with longer intervals between application and harvest than are necessary. The fact that very few samples contain residues in excess of the established tolerance demonstrates that the pesticides are typically used in compliance with regulations.

Since it appears that the majority of pesticide applications are performed legally, why is the issue of pesticides in the food supply a controversial one? Doesn't the regulatory system protect the consumers?

In the eyes of many, the system is inadequate. In California, which has the most extensive residue testing program in the world, approximately one percent of all food crops are tested for pesticide residues. While this is a relatively high testing rate compared with that used for meat and fish inspections or microbial monitoring, the residue monitoring program is effective as an enforcement tool but cannot ensure that populations will not be exposed to illegal residues. Recent cases involving human illnesses following consumption of watermelon and cucumbers containing illegal residues of the highly toxic insecticide aldicarb demonstrate that some hazardous levels of residues may go unchecked. Current legislation is aimed at increasing the rate of sampling. Even if the sampling rate were increased to five percent, which would cost millions of additional dollars annually, the majority of food would still not be subject to inspection, and the potential for illegal residues to make their way into the marketplace would not drop significantly.

Another major criticism of CDFA's program is that the multi-residue screen is capable of detection of only about one-third of all registered pesticides. While this screen may analyze for pesticides which account for 80 percent of all pesticide use in California, many argue that CDFA's claims that residue levels are typically very low are misleading since all the possible chemicals are not detected. CDFA chemists do have methods for the analysis of all pesticides registered in California, but most are specific for a single pesticide and are more costly and time-consuming than the multi-residue screen.

To verify that the levels of pesticides not detected using the multi-residue screen are consistent with those routinely analyzed, CDFA initiated in 1987 a Focused Monitoring program. This program analyzed 972 samples for the most potentially hazardous pesticides (as determined by the NAS report) that were not typically detected using the multi-residue screen. No residue was detected in 89.6 percent of the samples, while residues below the tolerance levels were detected in the remaining 10.4 percent of the samples. These results should not be surprising when one considers that levels of residues from legal applications should fall below the tolerance levels as a consequence of how the tolerances are established and that results from other monitoring programs have indicated that the vast majority of pesticide applications are made in compliance with regulations.

The tolerance system for pesticide regulation has also been called into question. Tolerances are established to ensure that pesticide applications are performed in compliance with regulations and that human exposure to pesticide residues is below the established ADI levels. These levels are set on the basis of the most sensitive toxic effects observed in laboratory animals, but do not apply to the ability of a pesticide to cause cancer. Of the 316 pesticides registered for foods in the United States, 55 are listed as suspected cancer-causing chemicals, or carcinogens.

Risks from carcinogens are determined differently than the risks from non-carcinogens. It is assumed, in the absence of scientific data to the contrary, that human exposure to a single molecule of a carcinogen may present a possibility, although probably miniscule, of causing cancer. As the dose of the carcinogen increases, the potential for the development of cancer increases.

According to the NAS report, under worst-case conditions, approximately 1.46 million cases of cancer in the United States could be caused by the residues of 28 pesticides. This figure is derived on the assumption that every pesticide registered on every crop is always applied to the crop and that humans consume residues at the tolerance levels on every food for 70 years. Risk assessments are performed using standard conservative procedures, which include making conservative (non-threshold) estimates of the ability of pesticides to cause cancers at low doses, and applying an upper 95 percent confidence interval to the estimates.

The risks calculated by the NAS are by no means indicative of the actual risks posed by exposures to pesticide residues in foods. As has been shown, typical levels of pesticide residues are far below the tolerance levels, and, in the majority of cases, may not be detectable. The assumption that all chemicals which are registered on a crop will always be used is also misleading.

The findings from the NAS report have indicated, however, that under the worst-case scenarios, residues from 23 different pesticides at the tolerance levels represent a cancer risk of greater than one excess cancer in every one million persons exposed throughout their lifetimes. This level of one in a million is often thought to represent the cutoff for a "significant risk" by the regulatory agencies. As a result of the NAS report, the EPA is currently considering legislation which would not allow use of a particular pesticide if exposure to the pesticide on all crops for which it were registered at the tolerance level could result in an increase of greater than one case of cancer in every one million persons exposed.

It is important that this "one-in-a-million" cancer be put in perspective with other common risks we experience. For example, the level of risk from eating one peanut butter sandwich per day or drinking one cup of comfrey herbal tea per day may be 500 times greater than the one-in-a-million level due to the presence of naturally-occurring toxins in the peanuts and comfrey. The risk posed by drinking tap water may represent a 100-fold greater risk (due to the presence of small amounts of chloroform which is a product of water treatment), while eating one raw mushroom per day may represent a 1500-fold greater risk, again due to the presence of natural toxins. These examples of naturally-occurring toxins are by no means inclusive; virtually every food item produced has been shown to contain some natural toxins and it has been estimated that the concentrations of natural toxins in foods are 10,000 times greater than those of synthetic chemicals. This is not to imply that there are no risks from pesticide residues in foods or that these risks are insignificant. The risks from pesticide residues represent involuntary risks, rather than voluntary, and residue levels should continue to be monitored regularly. Additionally, the potential exists for toxicity from illegal pesticide use, although studies have shown that the vast majority of pesticide applications appear to be in compliance with established regulations. These relative risks merely indicate that we must keep the risks from pesticide residues in perspective.

We should expect that the issue of pesticide residues in foods will remain highly controversial. It is anticipated that public concern will continue to mount and may ultimately cause changes in food consumption patterns or in the marketing of fresh produce. We have already seen examples of retail outlets certifying produce as "pesticide-free" following analysis by independent commercial laboratories. Public concerns are also reflected in pending California legislation, including AB 4097, authored by Connelly, D-Sacramento, which is aimed at increasing residue monitoring at the State level, and AB 3812, authored by Waters, D-Plymouth, which provides for CDFA accreditation of any commercial laboratory engaged in the analysis of foods for pesticide residues. At the Federal level, the practice of establishing tolerances for suspected carcinogenic pesticides is being called into question.

Concerns regarding food safety and pesticide residues are issues that are not going to go away. It is imperative that consumer and regulatory decisions concerning this topic are made on the basis of accurate and representative scientific information.

INTERNATIONAL TOXICOLOGY NEWS
Art Craigmill

Greetings from Julich, West Germany where I have been working in the Radioagronomy Institute of the Kernforschungsanlage (Nuclear Research Institute) of The Federal Republic of Germany for two months now, and finally have some time to put together a short article for the Environmental Toxicology Newsletter. I was back on the job during the month of March, however most of my time was spent with the ANR Reorganization, and simply catching up on the mail. Sandy Ogletree, the Extension Toxicology Administrative Assistant has been doing a great job of keeping the programs running in my absence, and Carl Winter at UCR has more than gotten his feet wet with Extension Programs while I have been away.

The reorganization of ANR, and the integration of Cooperative Extension into the Campus Departments has gone smoothly and satisfactorily here in Environmental Toxicology at Davis. I do not anticipate any major disruptions in program delivery, and do not see any reason why CE Advisor Training or program delivery to the counties should be affected. I am pleased to report that just prior to the reorganization, Lorry Dunning an SRA in Animal Science Extension, transferred to Toxicology Extension. Lorry began work for Toxicology Extension at the end of March, and during my absence has been working with Dr. Dave Hinton, in the Medicine Department of the School of Veterinary Medicine. Dr. Hinton is doing research on the toxic effects of chemical waste on fish growth and development, and Lorry is learning these techniques so that we can continue our work on pesticide waste treatment and collaborate with Dr. Hinton, using fish as test subjects for toxicity. After seven years without any SRA support, I am looking forward to having Lorry's help in this program, and other areas of work in Extension Toxicology.

The Kernforschungsanlage (Nuclear Research Institute) in Julich is a large research based organization which is funded both by the Federal Government, and also through grants and contracts from outside sources. The Radioagronomy Institute (IRA) has four major areas of research including pesticide fate in the environment, plant physiology, plant nutrition, and plant uptake of radionuclides from soil (stimulated considerably by the Chernobyl accident). The research that I have been pursuing here in the Radioagronomy Institute has to do with soil residues of pesticides. The term pesticide in Germany has a great similarity to the word Pest, which is German for Plague, and has a frightening connotation. Therefore, most scientists use the term "Pflanzenschutzmittel", meaning, plant protection materials, to avoid this connotation.

The IRA has been doing studies for several years on the fate of pesticides in soil*, using devices known as lysimeters. A lysimeter is essentially a large, stainless steel box or cylinder which is filled with soil, open on the top, and closed at the bottom so all liquid that runs through it can be collected. These lysimeters are kept both above ground, and in the ground, to simulate as much as possible, natural field conditions. The lysimeters range in size from 0.5 m2, to 1 m2, and are at least 1 meter deep, some of them almost 2 meters deep.

Crops are sown in the lysimeter soil to simulate planting densities common in Germany, and the lysimeters are kept outside and receive the same weather as regular fields. At different stages of plant development, the crops growing in the lysimeters are sprayed with pesticides which have been labeled with radioactive carbon, 14C. The 14C is incorporated into the pesticide molecule during its synthesis, and emits weak, but readily measured radioactivity. The total amount of radioactive material applied is known, and samples of the plants, soil and water (that percolates through the soil) can be taken and the level of radioactivity measured. In this way, the fate of the pesticide can be monitored over several years after single and multiple applications.

Not surprisingly, previous lysimeter studies have shown that pesticide residues in soil decrease at different rates depending on the pesticide applied, and the movement of the pesticide down through the soil (percolation) is also dependent on the type of pesticide applied. One major finding of these lysimeter studies is that some of the laboratory "bench-top" studies that measure percolation (and that are required by regulatory agencies for pesticide registration) do not give the same results as the lysimeters. In most cases, the "bench-top" studies show higher rates of percolation than do the lysimeter studies.

Another finding of these studies, which I find particularly interesting, is that some of the pesticide residues wind up as "bound residues", that is, they cannot be extracted by ordinary, or even extraordinary chemical means. This is a good time to introduce another major concept which is this; after applying any radioactive chemical to soil, when you measure the radioactivity, it may or not be in the same chemical form. That is to say, when you find radioactivity in bound residues, it may not be radioactivity from the pesticide itself, but from metabolites which contain the 14C. These metabolites can range from large molecules which are very similar to the pesticide, to "mineralized" metabolites in which the 14C may have been broken down to 14CO2, and then incorporated into sugars. The only way to know where the radioactivity is, is to chemically analyze the fractions which contain the radioactivity, something which is not always possible. The reason for using radioactive tracers in pesticide fate studies is the fact that it is possible to measure much lower levels than by using conventional chemical analysis. This is sometimes a Catch 22.

I have been doing analyses looking at bound residues of a herbicide called Methabenzthiazuron (MBT), which is registered for use in West Germany. Almost four years ago, MBT was applied to lysimeters here at the IRA, and the fate of the MBT has been followed in many ways. The overall depletion has been measured, the percolation has been measured, and during the last few years, bound residues have been determined. To determine the degree of bound residues in soil, a standard extraction technique has been used starting with extensive extraction with the organic (here used in the chemical sense of the word meaning "containing carbon") solvents acetone, ethyl acetate, and chloroform. This step takes three days to complete. All of the solvents are collected and the radioactivity measured, and the solvents concentrated so that the residues can be chemically analyzed. The soil is then extracted twice with a solution of sodium pyrophosphate, which is rather alkaline. The extract obtained is very dark, and contains substances known as humic and fulvic acids. The radioactivity in this fraction is counted, and then the humic acids are precipitated by making the solution very acidic (by adding sulfuric acid). In this way, the radioactivity associated with these various soil organic constituents can be measured, and chemically analyzed to see whether the parent compound (MBT) is still there. Previous work has shown that after two years, most of the radioactivity in the fulvic acid fraction is MBT, whereas much of the organic solvent extracted radioactivity is an MBT metabolite.

The radioactivity that remains in the soil after this exhaustive extraction procedure, is the actual bound residue, and it is almost impossible to know just what it is. It is unlikely to be MBT since it cannot be extracted with organic solvents, and is likely to be 14C from the extensively metabolized MBT. One of the major discoveries from these and other lysimeter studies, is the finding that pesticide residues appear to enter into the soil carbon cycle, and are metabolized, transported, bound, and released just like organic compounds (like straw) that have been worked into the ground as a result of agricultural practices.

There are of course many more questions than there are answers in this area, and as with most good research, the more that is learned, the more questions there are. The question that I am currently looking at is this; does the extraction procedure itself have an effect on the distribution of residues in fulvic acids, humic acids, and bound residues? It is entirely possible that the extraction procedure produces an artificial distribution of the radioactivity in the soil fractions. Another way to say this is that the procedure itself is affecting the results, so I am looking at an alternative method of extraction.

As a toxicologist with much more research experience with animal systems than with plants or soil, this has been a very educational experience. Working with animal systems is far easier than working with soil! Animals have a certain degree of uniformity, or at least you can raise them to be rather uniform. Soils can vary considerably from field to field, and even within a single field. In addition, where animals fairly well maintain homeostasis (constant temperature, health, etc.), soils are quite dependent upon weather conditions. It is also very easy to find different parts of animals (liver, kidney, brain). In the soil, these components are are intermixed and can be difficult to separate. The soil however is a living system, with very complex interrelationships. Many of the principles that apply to animals apply also to soils, that is, there are some very definite similarities especially in the area of kinetics (distribution, metabolism, transport). The opportunity to work here has been quite enlightening, and has provided me with useful information that I will be able to apply to our future extension field work in the area of pesticide waste disposal and disposal site cleanup.

Organophosphate Toxicity Associated With Flea-Dip Products - California

Flea-control products, particularly flea dips for pet animals, may contain potent cholinesterase-inhibiting organophosphate pesticides. In 1986 and 1987, two cases of human illness associated with the use of flea-dip products were reported to the California Department of Health Services (CDHS) and the California Department of Industrial Relations (CDIR).

Case 1

In early September 1986, a 33-year-old female pet groomer complained of periodic headache, nausea, dizziness, tiredness, and blurred vision and of sweating and feeling "confused" and "spaced out". For over a year, these episodes had occurred more frequently, and the symptoms had become more severe each time. According to her friends, her pupils were often pinpoint-sized during these episodes. At first, she thought her symptoms were due to stress at work, and she did not seek medical care.

For the preceding 18 months, she had been treating dogs with an organophosphate pesticide. During the summer months, she had treated an average of 10 dogs per day. The flea-dip product she used is a liquid concentrate containing 11.6% phosmet (a cholinesterase-inhibiting organophosphate insecticide known to cause acute irritation of the mouth, eyes, and skin) as the active ingredient. While diluting the concentrate in water, she frequently had spilled some of the concentrate on her skin.

After consulting with HESIS, the woman's physician diagnosed her illness as organophosphate intoxication. Her red cell cholinesterase activity (0.84 pH) was well within the usual range (0.56-1.01 pH) found by the testing laboratory. The woman was treated with oral atropine, and her symptoms diminished. For 2 weeks after returning to work, she avoided contact with flea- dip solutions and remained asymptomatic; however, within an hour after she treated a dog with a product containing chlorpyrifos, a mild-to-moderate cholinesterase-inhibiting agent, her symptoms recurred. After that, she avoided contact with all organophosphate pesticides. Seven months later, her level of red cell cholinesterase, measured by the same laboratory, was within 20% (0.67 pH) of the first value.

Telephone Survey

Later in September 1986, HESIS conducted a telephone survey. Twenty-four pet groomers in the San Francisco Bay area and Los Angeles were selected at random from listings in telephone directories. Through telephone interviews, 12 persons reported that they frequently used flea-dip products and usually had symptoms when they worked with the products. The symptoms most commonly reported were headache, dizziness, nausea, fatigue, and dermatitis. Two persons reported having symptoms of sweating, tearing, and confusion, all of which are consistent with cholinesterase inhibition. Flea-control products containing phosmet were most often reported as being related to the symptoms. One person complained of symptoms while working with a product containing chlorfenvinphos, an organophosphate classified by the Environmental Protection Agency (EPA) as Toxicity Class 1 (the most toxic chemicals are assigned to Class 1).

Most of the pet groomers reported that they did not wear aprons or gloves and did not use the pesticides according to directions on the product labels. They often applied the undiluted concentrates with bare hands, and their skin and eyes were frequently exposed to the flea-control products.

Case 2

One of the persons interviewed was a 43-year-old female dog groomer who had been treating 8-12 dogs each day for 3 years. She sponged a concentrated solution of flea-dip product directly onto flea-infested areas on the dogs. For a year, she had had periodic dizziness, fatigue, blackouts, blurred vision, chest pain, sweating, coldness, and chills. During these episodes, she had pinpoint-sized pupils. Because of the blackouts, her physician referred her to a neurologist, who observed that she had unequal pupils during one of these episodes. Diagnostic tests - including an electroencephalogram and a brain scan - did not reveal the cause of her symptoms. Pesticide poisoning was not suspected until HESIS referred her to a physician specializing in occupational medicine. Three months later, after she had completely avoided all exposure to the products, her red blood cell cholinesterase levels had gradually increased by more than 30%. The majority of her symptoms also resolved during this period. On the basis of this finding, her illness was diagnosed as organophosphate pesticide poisoning.

Further Investigations

CDHS is now conducting a statewide investigation of pet groomers and other animal handlers. The California Department of Food and Agriculture is evaluating the hazards, use, and labeling of all flea-control products containing phosmet.

Editorial Note: EPA has assigned phosmet to Toxicity Class II because of acute oral toxicity (LD50 = 147 mg/kg). In a recent review of registration data on pesticides, investigators found a lack of information on acute inhalation toxicity, subchronic dermal toxicity, mutagenicity, oncogenicity, and the general metabolism of phosmet. The low-level, acute dermal toxicity (LD50 - 3,160 mg/kg) suggests a low rate of dermal absorption, but quantitative data on dermal absorption - particularly of flea-dip formulations - are lacking.

EPA requires that products used as flea dips for dogs and cats must have labels cautioning the users to wear long-sleeved shirts, long pants, elbow-length waterproof gloves, waterproof aprons, and unlined waterproof boots. Because animals that have been dipped or sprayed with pesticides have become ill or have died, EPA now requires that the product label state that a dog or cat may be poisoned if the product is not properly diluted before use.

The extent to which animal handlers in the United States are exposed to or become ill from flea-control pesticides is unknown. Animal groomers and handlers should follow label directions precisely and should wear gloves and protective clothing as recommended.

Art Craigmill Note: It is no surprise that not following directions for pesticide use can lead to injury, yet many people still have the unique ability to not only ignore directions, but also to be surprised when they become ill!

MMWR, June 3, 1988, Vol. 37 / No. 21.

Carl Winter
Extension Toxicologist
UC Riverside
714-787-5994

Art Craigmill
Extension Toxicologist
UC Davis
530-752-2936