PESTICIDES AND THE IMMUNE SYSTEM - OVERVIEW

by Dr. Robert Repetto and Sanjay Baliga
(Pagenumbers refer to corresponding sections in the report.)

OVERVIEW

A wide variety of evidence indicates that exposure to many common pesticides damages the human immune system, weakening the body's resistance to infectious diseases and certain cancers. This serious public health concern is being neglected.

An urgent program of research and regulatory attention is needed to clarify and respond to this risk, which may well be exacerbating sickness and death worldwide.

THE PROBLEM

Hundreds of studies using accepted scientific methods have shown that many pesticides alter the immune system in experimental animals and make them more susceptible to disease. Pesticides have been found to reduce the numbers of white blood cells and disease-fighting lymphocytes and impair their ability to respond to and kill bacteria and viruses. They also alter the development of the thymus and spleen, key immune organs. (p. 21)
Studies have documented these effects for many pesticides used in this country and worldwide: organochlorines (e.g., DDT, lindane, chlordane), organophosphates (e.g., malathion, parathion, diazinon), carbamates (e.g., aldicarb, carbofuran, carbaryl) and others (2,4-D, atrazine, captan). (p. 18-20) Most pesticides now on the market have never been adequately tested in the laboratory for immunotoxic effects. (p. 4)
Few studies have assessed the impact of pesticides on the human immune system, partly because such research is extremely difficult to design and implement. Although most people are exposed to chronic low concentrations rather than the high doses used in laboratory tests, no basis exists for assuming that humans are exempt from risk.
Epidemiological studies from Canada and the former Soviet Union find that children and adults exposed to pesticides suffer similar immune system alterations and higher rates of infectious disease. The risks of pesticide-induced immunosuppression are known to be greatest to infants and children, the aged, people malnourished or chronically ill. (p. 18, 56)
Pesticide production is a $30 billion industry, and 62 percent of sales is in the United States,Western Europe and Japan. But pesticides are applied intensively in parts of the developing world and use there is growing more rapidly. (p.3)
The acute toxicity and possible cancer risks of many pesticides have led to bans or use restrictions in the U.S. and Europe. Many of those pesticides are still being produced and used in the developing world and in the former Soviet Union. (p. 4)
Hundreds of millions of people are significantly exposed to pesticides every day, either directly in farm and garden use or in residues in water, air and food. Direct bodily measurements of exposure show that even children in rural areas and infants breastfeeding from exposed mothers can receive substantial doses. (p. 9-16)
As much as 85 to 90 percent of pesticides applied to agriculture never reach their targets, but instead disperse into the air, soil and water, and into the bodies of nearby animals and people. (p. 13) Farmers and rural residents are immediately exposed, but faraway consumers of agricultural products and fish are also at risk. (p. 9-15)
Pesticides that accumulate up the foodchain are still used in many countries. Measurements of the blood, fat and breast milk of people far from agricultural areas often show significant pesticide residues and enzyme depletions caused by certain pesticides. Far in the Arctic, Canadian Inuits carry as high a concentration of these compounds in their fat as polar bears and beluga whales do. (p. 49)

THE WORLD RESOURCES INSTITUTE SURVEY

Therefore, in an effort to survey the issue of pesticides' human immune system effects, The World Resources Institute drew upon a number of sources:

Previously unpublished and/or confidential data on pesticide use patterns worldwide;
A wide range of information on pesticide exposure levels;
Experimental, laboratory, and wildlife evidence of effects on the immune system of animals;
The few human epidemiological studies, most of which are new or little known in the English-language literature--especially studies from the former Soviet Union and northern Canada;
Evidence of synergies between chemical exposure and other risks to the immune system, such as malnutrition, chronic disease, and age; and
Prospects for current and future research programs and the need for further action.

THE FINDINGS

The mortality rate from the common infectious diseases, already by far the biggest killer in developing nations, may be driven in part by pesticide exposure.

Communicable diseases cause nearly half of all deaths in the developing world, compared to less than 10 percent in industrialized nations. (p. 55) Chronic malnutrition, inadequate health services, and poor sanitation are already serious threats to health. Any additional impairment of natural immune defenses can kill.
In developing nations, controls over pesticide marketing, manufacturing, and use are typically weak. Safety precautions are widely ignored. Symptoms of overexposure such as respiratory trouble, gastric upset, rashes, dizziness, "nerves" and weakness are usually disregarded or misdiagnosed. Doctors in the field found pesticide overexposure three times as common as farmers themselves reported. (p. 11)
In central Luzon in the Philippines, pesticide use rose dramatically in one five-year period, and mortality rates rose directly with it among adult male farmers. The rate fell for adult females in the same villages and for males in nearby towns. (p. 40)
Isolated Canadian Inuits who eat mainly fish and marine mammals heavily contaminated with accumulated pesticides show pronounced immune system deficiencies, particularly among breast-fed infants and children. Meningitis and inner ear infections occur at rates 30 times that of American children. Many Inuit babies can't be vaccinated, since they don't produce an antibody response. (p. 48-49)
Tuberculosis has grown dramatically in Central Europe and the former Soviet Union where chemical pollution is widespread. (p. 56) Tuberculosis outbreaks are common among immunosuppressed groups.
Cotton workers in Uzbekistan had impaired cell-mediated immunity and suffered higher rates of respiratory, kidney and intestinal infection than residents of other areas using fewer pesticides. (p. 40, 45)
Children are particularly susceptible to the effects of pesticides on their immune systems. In the agricultural districts of central Moldova, where pesticides have been used heavily, 80 percent of healthy children had suppressed immunity. Children from these areas were three times more likely to have infectious diseases of the digestive tract, and two to five times more likely to have infectious diseases of the respiratory tract. Workers in pesticide factories and on farms in the area exhibited elevated rates of infectious diseases of the digestive, urinary, respiratory, and female genital tracts. (p. 47-48)
Indian factory workers chronically exposed to pesticides showed a 66 percent drop in blood lymphocyte levels, but tested normal after three months' vacation. (p. 46)
A recent plague that killed dolphins in the Mediterranean, the North Sea and the North Atlantic turned out to be common viruses to which the animals were normally resistant. Blood samples from dolphins off the Florida coast showed the mammals had high levels of pesticide residues, major viral infections and weak immune systems. (p. 36)
Seal pups captured off the relatively unpolluted Northwest coast of Scotland were fed uncontaminated fish for one year. Half were then fed herring from the polluted Baltic sea. These seals developed high bodily concentrations of pesticides and other organochlorine chemicals and immune system responses a third as strong as in a control group. (p. 36-37) The herring was purchased from local markets and had been intended for human consumption.
Pesticides may increase susceptibility to certain cancers by weakening the immune system's surveillance against cancer cells.
Autopsies on dead whales from the highly contaminated St. Lawrence Seaway found high tissue concentrations of certain pesticides and PCBs, as well as severe bacterial infections and frequent tumors. (p. 36)
Farmers generally have lower risks of cancer than other men, but have a higher risk for the kinds of cancers found in immune-deficient patients (those with AIDS and those taking immuno-suppressive drugs): Hodgkin's disease, melanoma, multiple myeloma, leukemia (all cancers of the immune system) and cancers of the lip, stomach and prostate. Farmers most heavily exposed to pesticides have the highest relative rates. (p. 41-42)

Some pesticides are linked conclusively to the production of auto-immune antibodies, attacks of the body upon itself. (p. 43-44)

Russian research in the cotton, tobacco and vegetable-growing regions of Samarkand found that people exposed to organo-chloride and organo-phosphate pesticides harbored auto-immune antibodies. Factory workers elsewhere in Russia showed similar symptoms. (p. 44)

RECOMMENDATIONS

The World Health Organization should take the lead in designing and organizing an extensive program of research to address the risk of pesticide damage to the human immune system.

Member governments should provide the necessary financial support since little or no funding has been allocated for such research in national budgets. Research funding is instead being cut worldwide.
The U.S. Agency for International Development (USAID) should support epidemiological research on pesticides' health risks to vulnerable populations as part of its work in developing countries.
Multilateral development banks should support this research to bolster their investments in water supply, sanitation and primary health care systems in developing nations.
Major pesticide companies have a responsibility to ensure that the products they sell do not pose immunotoxic risks. They should join and support these research programs and take steps to minimize the health risks from their products.
Government regulatory agencies should substantially strengthen their surveillance and control over the use of potentially immuno-toxic pesticides.
Thorough testing for immuno-toxicity should be required as a condition of continued registration of products for sale.
Agriculture ministry training and extension programs in safe pesticide use should be improved and expanded.
Integrated pest management programs of research and extension should be expanded in order to encourage farmers to reduce pesticide use.
A fee per kilogram of active ingredient on pesticides sold would be one way of financing budget increases for these programs in developing countries that now do not have health and safety regulations or the capacity to enforce them.

Copies of Pesticides and the Immune System: The Public Health Risks are available for $14.95 plus $3.50 for shipping and handling from WRI Publications, P.O. Box 4852, Hampden Station, Baltimore, MD 21211, 1-800-822-0504 or 410-516-6963. Complimentary copies are available for journalists from Adlai Amor, 202-729-7734.

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