UNIVERSITY OF CALIFORNIA
ENVIRONMENTAL TOXICOLOGY NEWSLETTER
Vol 12 / No 2 - May 1992
Table of Contents
- Land Disposal of Sewage Sludge
- MSG Update
- Blood Lead Levels Among Children in High-Risk Areas - California, 1987-1990
- Update on Nitrofurans
- Waste Management Materials
The title of this issue is taken from the feature article written by Marylynn Yates. It is a particularly appropriate topic. Despite a continued water shortage, there is no shortage of sludge generated by the millions of Californians. Dr. Yates serves as a member of the U.C. Waste Management Workgroup which has been collecting information for use by county advisors, and soon there should be a waste management specialist at UCR to further coordinate the activities statewide. A few bits of information about waste management programs in other states are included at the end of the newsletter. Please call if you need information about waste management options for your county. Waste management will be one of the biggest problems we have to face in California during the next few years.
The MMWR recently had an article with direct relevance to California's children and risk of lead intoxication. Jeanette Sutherlin and Nancy Feldman recently coordinated a lead testing training session in Fresno, and we discovered three Mexican pottery pieces (two of them in use) which leached high levels of lead.
Also included is a short update on MSG and a note concerning the use of nitrofuran drugs on dairies. In addition, in response to an assertion that toxicologists have warped senses of humor, we include a poem from a Poison Center (which basically proves the assertion is correct).
A copy of the 1990 report from the Department of Pesticide Regulations on RESIDUES IN FRESH PRODUCE has been sent to every county office. If you need it and cannot find a copy, please call and we will send one right away.
LAND DISPOSAL OF SEWAGE SLUDGE
Dr. Marylynn Yates
There are several factors that need to be considered when thinking about applying sewage sludge to land. Some of these are related to the presence of microorganisms that can cause disease in humans (hereafter referred to as pathogens) who are exposed to them. Some important facts that you should be aware of are listed below.
Pathogens (especially parasites and, to a lesser extent, viruses) can survive in the environment for a considerable period of time (months to years).
Sewage treatment processes do not completely inactivate (render harmless) all pathogens that may be present in sewage sludge.
The number of pathogens is reduced during each stage of sewage (sludge) treatment. However, even composted sludge cannot be guaranteed to be free of all pathogens.
For human pathogenic viruses (such as hepatitis A virus and poliovirus) and some pathogenic parasites (such as Giardia and Cryptosporidium) the number of microorganisms that must be ingested to cause disease is very small - in some cases only one particle may cause disease.
The absence of fecal coliforms or fecal streptococci in sludge does not guarantee the absence of pathogenic microorganisms. Many pathogens are much more resistant to inactivation by sewage and sludge treatment processes than are the so-called indicator bacteria.
Viruses have been detected in ground water beneath sites where sewage sludge is being applied.
Certain parasites (such as tapeworms) that may be present in animal waste can also pose a threat to human health. There are several environmental factors that influence the potential for human exposure to pathogens in sludge.
Viruses are inactivated (killed) more rapidly at high temperatures than low temperatures.
Exposure to ultraviolet (UV) light (in sunlight) can reduce the number of viruses and bacteria; however, parasites are much less susceptible to inactivation by UV light. Therefore, allowing the sludge to remain on the land surface before discing it into the soil will reduce the number of pathogens. The drawback to this is that there can be fly and odor problems if the sludge is left on the surface. There can also be problems with airborne transmission of the pathogens.
Shallow ground waters are more vulnerable to contamination than deep ground waters.
Coarse-textured or fractured soils allow pathogens to be transported more readily than fine-textured soils.
Areas with high rainfall and/or that irrigate have a higher potential for ground or surface water contamination because pathogens can be carried with the water.
Obviously, all of the above are generalities, and the interactions between these factors must be considered for a given site. A very general description of a site that would have a relatively high potential for human exposure to pathogens might be as follows: application of liquid sludge to a sandy soil with a shallow (less than 50 ft) water table in a cool environment. Domestic wells in close proximity to the sludge-applied land, especially if down-gradient, may be vulnerable to contamination.
Careful site selection and management of sludge application combined with monitoring of the sludge quality can lead to a beneficial use of material that would otherwise be wasted. However, you must keep in mind that there is no such thing as a zero-risk situation.
Anyone who would like more information on the topic of pathogens in sludge, or reclaimed water for that matter, feel free to call. I will be happy to provide references that substantiate these statements and provide more details. (714-787-5488; FAX - 714-787-3993)
What is MSG?
MSG is the sodium salt of glutamic acid. Glutamic acid or glutamate is one of the most common and important amino acids found in nature. Glutamate is produced in the body and plays an essential role in human metabolism and other vital functions. It is virtually ubiquitous in the diet as a component of many protein-rich foods such as cheese, meat, fish, milk and some vegetables. When present in its "free" form - not bound tog ether with other amino acids in protein - glutamate has a flavor- enhancing effect in foods.
When MSG is added to foods, it provides a similar flavoring function as the naturally-occurring free glutamate. MSG contains only one-third the amount of sodium as salt and is used to enhance the natural flavors of meats, poultry, seafood, soups and stews. This distinctive flavor is known as "umami." Westerners often describe this flavor as savory, broth-like or meaty.
According to Susan Schiffman, Ph.D., professor of medical psychology at Duke University, recent psychophysical studies have confirmed the age-old Eastern belief that MSG imparts a unique fifth taste. Multidimensional scaling experiments, which form the basis of sensory research, indicate that MSG falls outside the region occupied by the four classic tastes of sweet, sour, salty and bitter.
Emerging dietary research also points to MSG's potential to enhance food intake in the elderly. Deterioration in the senses of both taste and smell that accompany aging often contribute to poor nutritional status. A recent study found that moderate levels of added MSG in foods such as mushroom soup and mashed potatoes enhanced food intake in an institutionalized elderly population.
MSG was designated by FDA in 1958 as a GRAS substance, along with many other common food ingredients such as salt, sugar and baking soda. Hundreds of biochemical, toxicological and other studies over many years have found MSG to be safe for the general population including pregnant and lactating women.
Research conducted at the University of Iowa shows that one-year- old human infants can metabolize glutamate as effectively as adults. They can also detect the taste of free glutamate, which is 10 times more plentiful in human breast milk than cow's milk.
There is no scientific evidence to suggest that MSG causes attention deficit hyperactivity disorder or other behavioral problems in children.
In the early 1970s, concerns were raised by some individuals that a diet extremely high in MSG could adversely affect the brain. However, there is no scientific evidence that MSG consumed in levels in foods could affect cognitive function or pose other public health risks.
Europeans Say MSG Safe
In June 1991, the Scientific Committee for Food of the European Communities reaffirmed MSG as safe. The committee established MSG's acceptable daily intake as "not specified," the most favorable designation for a food ingredient.
MSG also has been placed in the safest category of food additives by the Joint Expert Committee on Food Additives of the United Nations Food and Agricultural Organization and the World Health Organization.
The current database supports the conclusion that MSG has been a safe and useful component of our food supply since the turn of the century.
The phrase "Chinese restaurant syndrome" was coined in 1968 to describe a collection of symptoms allegedly experienced after eating Chinese food. These reactions include warmth, tingling, and a feeling of pressure in the face and upper chest muscles.
"There have been numerous challenges of MSG-induced adverse reactions in individuals, all of which have failed to reproduce the symptoms associated with Chinese restaurant syndrome," said Steve Tayl or, Ph.D., professor and head of the Food Science Department at the University of Nebraska. Studies measuring objective responses such as blood pressure, heart rate, skin temperature and muscle tone have been unable to detect differences between persons fed MSG and placebo.
Nonetheless, anecdotal reports suggest that a small percentage of the population may be sensitive to MSG. These reactions tend to be mild and transitory. MSG-sensitive individuals should contact their physician or a certified food allergist to participate in double-blind, placebo-controlled studies to determine the origins of their discomfort.
New Labeling Proposal
Currently all foods with added MSG must list the ingredient on the label as monosodium glutamate. FDA recently announced it may broaden the requirement to require listing of glutamate when it is a significant functional component of other ingredients such as hydrolyzed protein.
In announcing the change, FDA underscored that the decision is due to public interest in the issue and not from any health concern about MSG's safety. The tentative final regulation is expected to be published in mid-1992.
Reference: Food Insight, January/February 1992.
When the Law is a <169>Yolk<170>
A law was passed in a certain state, New
Jersey, I think's the one;
concerning the eggs upon my plate,
and how well they must be done;
No more soft-boiled, no longer runny,
not easy-over nor poached,
I must admit I think it's funny,
but each cook must soon be coached;
They'll need a timer and other stuff,
that'll notify the fella',
that he's cooked the eggs long enough,
to get rid of salmonella;
So if you think we've gone too far,
with these laws and government regs,
remember that our springtime star -
the Easter Bunny - gives hardboiled eggs.
Ralph Lucanie RPh
Hudson Valley Poison Center
Reference: Vet Hum Toxicol 34 (2), April 1992.
BLOOD LEAD LEVELS AMONG CHILDREN IN HIGH-RISK AREAS - CALIFORNIA, 1987-1990
In the United States, elevated blood lead levels (BLLs) are a major health risk for children; this risk is totally preventable. To better characterize lead poisoning among children at high risk for lead exposure in California, the California Department of Health Services (CDHS) conducted lead-screening surveys that measured lead levels in children's blood, household paint, and soil in three selected high-risk areas in northern, southern, and central California. This report summarizes the survey findings and describes CDHS's efforts to reduce lead exposure among children in California, especially among those in high-risk areas.
CDHS selected three areas for the surveys based on the likelihood that old housing in these areas contained lead paint (42%-72% of the housing in the survey areas was built before 1950): Oakland in Alameda County (1987); Wilmington and Compton in Los Angeles County (1988); and Sacramento in Sacramento County (1990). In the Oakland and Sacramento survey areas, CDHS attempted to enroll all households with children aged 12-59 months. In the two communities in Los Angeles County, a systematic sample of every fourth block was selected, and CDHS attempted to enroll all households with children aged 12-59 months in those sample blocks. The proportion of eligible households agreeing to participate in each area included 358 (71%) of 506 in Oakland, 350 (56%) of 621 in Wilmington/Compton, and 232 (47%) of 495 in Sacramento. Overall, these households included 973 families with 1397 children in the target age range (ages of children were equally distributed).*
*In Los Angeles County, of 471 children surveyed, 272 were excluded because the blood collection tube lot used for their samples was later found to be contaminated with lead; the remaining 199 children included in the study had household environmental lead levels and demographic characteristics similar to those of the excluded children. Paint and soil lead levels are presented for all 350 households.
In Oakland, initial blood lead testing was performed by collecting capillary blood samples from the children. To reduce the possibility of sample contamination caused by lead on children's hands, their hands were vigorously washed before the capillary sample was obtained; a confirmatory venous sample was obtained from 74% of the Oakland children with an initial capillary BLL >15 ug/dL. In Wilmington/Compton and Sacramento, venous blood samples were collected from 96% of the participating children; capillary samples were collected from the other 4% of children surveyed.
In Oakland and Wilmington/Compton, household paint samples were collected only when peeling or chipping paint was observed; in Sacramento, paint samples were collected from surfaces regardless of condition. At each household, soil samples of the top inch of soil were collected from one to five locations (i.e., midsection of front, back, and side yards; directly beneath a rain drain; and near a building not attached to the house on the household property); soil lead level was defined as the geometric mean of all samples collected at the household. Paint lead levels reported were the maximum level found at a home. Lead content in blood and environmental samples was measured using graphite-furnace atomic-absorption spectrophotometry.
In these three areas, 40%-84% of children were Hispanic and members of families with reported annual family incomes of <$15,000. BLLs of >10 ug/dL1 were detected in 67% of children in Oakland, 32% in Wilmington/Compton, and 14% in Sacramento. BLLs >20 ug/dL2 were detected in 5% of children in Oakland, 4% in Wilmington/Compton, and 1% in Sacramento.
Geometric mean lead levels in household paint were highest in Oakland and lowest in Wilmington/Compton (range for exterior paint: 3100-13,545 parts per million (ppm). In all three areas, exterior surfaces were substantially higher in paint lead levels than were interior surfaces. However, lead levels for some interior paint samples exceeded 5000 ppm (37% in Oakland, 25% in Sacramento, and 13% in Wilmington/Compton).3 Soil lead levels were highest in Oakland where 46% of household soil lead levels exceeded 1000 ppm.
1 Levels at which adverse health effects in children have been demonstrated.
2 Levels high enough to require medical evaluation according to CDC guidelines.
3 According to guidelines established by the U.S. Department of Housing and Urban Development, surfaces with paint lead levels of >5000 ppm should be abated during comprehensive modernization activities.
Editorial Note: Because recent research findings indicate that adverse health effects may occur among children with BLLs >10 ug/dL, CDC guidelines recommend actions to reduce lead exposure in communities where such levels are prevalent. Before the CDHS assessment, the potential risk for childhood lead poisoning had not been widely recognized in California or other western states. However, the CDHS findings summarized in this report indicate a high prevalence of elevated BLLs among children in high-risk communities in California and are consistent with reports elsewhere. Although many children participating in these surveys had BLLs that exceeded the guidelines, the levels were too low to cause overt symptoms; thus, in the absence of the CDHS survey, the high prevalence of this problem in Oakland may not have been recognized.
Lead-based paint, the most common source of high-dose lead exposure for children, was present in a high proportion of the dwellings surveyed by CDHS. In the western U.S. census region, an estimated 80% of privately owned housing units built before 1980 contain some lead-based paint, and the prevalence and concentration of lead in paint is proportionate to the age of the housing units. In California, an estimated 560,000 children aged <6 years reside in housing units built before 1950 that probably contain high levels of lead in paint.
In addition to lead-based paint, there are at least three other important potential sources for lead exposure in California. First, lead-contaminated soil was common in the communities surveyed; in urban areas, such contamination may result from deteriorating exterior lead-based paint and/or from emissions from automobiles using leaded gasoline. Second, in California, seven secondary lead smelters may contribute to contamination of nearby soil. Third, in addition to environmental sources, the use of folk medicines and pottery containing lead is prevalent among some minority groups and has caused severe cases of childhood lead poisoning.
In January 1992, the use of leaded gasoline was banned by law in California. In addition, CDHS is exploring other strategies to remove lead from consumer products and to identify and remove lead hazards from high-risk communities. The CDHS is implementing a comprehensive lead-poisoning prevention program that includes periodic blood lead testing for children aged <<6 years; case management by local health agencies; laboratory-based reporting; and educational programs for local health departments, health-care providers, and the public. During 1992, CDHS has been preparing regulations for residential lead-paint abatement. CDHS also is implementing strategies to reduce occupational lead poisoning, prevent the use of lead-based folk medicines, and eliminate other sources of lead exposure.
Reference: MMWR, Vol. 41/No. 17, May 1, 1992.
UPDATE ON NITROFURANS
A September 6, 1991, CVM Update discussed a Federal Register announcement on FDA's withdrawal of approvals for two nitrofuran animal drugs (furazolidone and nitrofurazone) used in food- producing animals. This withdrawal affected products that were approved for a variety of conditions in poultry and swine. The CVM Update also stated that CVM planned to add nitrofurans to the list of drugs not allowed for use under the extralabel drug use policy (CPG 7125.06). FDA is in the process of revising the CPG to reflect the Commissioner's conclusion that the nitrofuran drugs are unsafe for oral or parenteral use in food-producing animals. Nitrofuran drugs are being listed with those of highest priority for regulatory attention regarding extra-label use in food-producing animals. The CPG will prohibit the use of furazolidone, nitrofurazone, or other nitrofurans in food- producing animals, except for topical preparations approved for such use.
There are only two topical nitrofurans approved by FDA for use in cattle. They were not affected by the withdrawals and will not be added to the list of prohibited drugs in CPG 7125.06. These drugs are:
(1) Furazolidone aerosol powder (Trade names such as Topazone and Furox aerosol.)
(2) Nitrofurazone topical powder for pinkeye and wounds (Trade names such as NFZ Puffer and P.E. 7.)
There are solutions, ointments, and creams that contain furazolidone or nitrofurazone labeled for topical use in horses, dogs, and cats, and for intrauterine use in horses. They are often used in an extra-label manner to compound mastitis mixes and treat metritis in dairy cattle. Any use of these non-cattle topicals in food-producing animals constitutes extra-label use. Under the revisions to CPG 7125.06, such extra-label use is unacceptable and will draw the highest priority for regulatory attention.
Item 16r of the Pasteurized Milk Ordinance states that topicals are exempt from the labeling and storage requirements unless they are intended for direct injection into the teat or it is determined that they are stored in such a manner that they might contaminate the milk or milk product surfaces. The Ordinance also states that unapproved drugs should not be used to treat dairy animals. The revisions to CPG 7125.06 will make the use or storage on dairy farms of any nitrofuran drug (except the approved cattle topicals) a violation of item 16r of the PMO.
Reference: FDA Veterinarian, Vol. VII, No. III, May/June 1992.
Waste Management Materials
The following is a list of programs and materials that were announced in the USDA-Extension Service National Initiatives Waste Management Newsletter. If you would like additional information about any of these materials, please contact Sandy Ogletree at 916-752-2936.
Arthur L. Craigmill, Ph.D.
University of California
Davis CA 95616-8588