Effects of Pesticides
Much facts remains unknown about the effects of pesticides, pesticide mixtures and pesticides mixed with other chemicals or drugs on particular physical conditions and illnesses. There is a lot of controversy surrounding pesticides and their possible effects as carcinogens, mutagens and allergens. There have been many claims and counter-claims about the theory that pesticides at very low levels in food may produce allergic responses.
And also, we still do not fully understand and in some instances, have barely started to research the possibilities of pesticides at very low levels causing changes in the human immune system, damaging human reproductive capacity or adversely affecting our neurological system.
Pesticides like paraquat and maneb have been associated with Parkinsonís disease but no conclusive evidence is available to prove or disprove a causal link between exposure and disease.
The consequences of using pesticides have concerned scientists exactly because pesticides are biologically active substances which are deliberately and not accidentally introduced into the environment. This use may then lead to the presence of pesticide residues in food, and the presence of pesticides in water and air.
What is indisputable is that large numbers of pesticides have been detected, albeit often at very low levels, in many foodstuffs sold throughout the world. There have also been a number of epidemics of acute pesticide poisonings in the past due not to low- level residues of pesticide in food but to pesticide spill ages or grain treatments.
Wales, Egypt, India, Malaya, Turkey, Pakistan, the US and several other countries have all experienced such pesticide food poisoning epidemics. In Wales, flour contaminated by endrin caused 159 poisoning cases; in Qatar such flour caused 691 poisonings and 24 deaths. Parathion in wheat poisoned 360 and killed 120 and the same chemical in flour poisoned 600 and killed 88 in Colombia. In Turkey the consumption of seed grain treated with HCB poisoned over 3,000 and between 3-11% of those died.
By 1969, 17 pesticide food epidemics had been recorded. The effects of acute poisoning are relatively easy to diagnose and record: the effects of low-level exposure are not.
It will take many years in most countries to assess those pesticides cleared in the past when testing standards were less complete and rigorous than they are now. An indication of the serious nature of the gaps came in 1984 when the US General Accounting Office (GAO) found that of 92 pesticides in one of its studies, 62% had data gaps on tumours and 73% had data gaps on birth defects.
Some scientists think that pesticides at low levels are a causal factor in several diseases and may be linked to food chemical sensitivity: others do not.
The more conservative estimates suggest that worldwide there are hundreds of thousands of cases of pesticide poisoning and tens of thousands of deaths from pesticide exposure. One estimate from the WHO/UN Environment Programme indicates that there could be up to one million cases of unintentional poisonings from pesticides each year. In countries like Sri Lanka, the Philippines and other Central American and South East Asian states, occupational and environmental health problems created by pesticide usage are now major causes of illness and death.
The main pesticide chemical groups have known acute effects and sometimes either unknown or potentially serious chronic effects.
Organophosphorous insecticides are neurotoxic and have affected the human nervous system and may cause protracted peripheral neuropathy. Others have been linked to mutagenicity and animal carcinogenicity.
Organochlonnes have caused concern because of their long-term persistence in the environment, storage in body fat and carcinogenicity in test animals. They can also interfere with the metabolism of chemicals and can affect the nervous system at high doses.
Chlorophenoxy herbicides have been linked with potential carcinogenicity, neurological effects and teratogenicity.
Growing evidence demonstrates that pervasive contamination of air, water, soil and food with a wide range of industrial carcinogens, generally without public knowledge and consent, is important in causation of modern preventable cancer. Even if hazards posed by any industrial carcinogen are small, their cumulative, possibly synergistic [combined effect being greater than single chemical effect] effects are likely to be substantial. Eating food contaminated with residues at maximum legal tolerances of only 28 of 53 known carcinogenic pesticides, excluding numerous other carcinogenic pesticides and incremental exposure in drinking water, is estimated to be potentially responsible cancers.
Those who study patterns of disease, epidemiologists, have great difficulty in taking into account all the factors which might explain the trends in cancer mortality and morbidity. Many such studies produce negative results but this does not mean that they have proved chemicals do not cause cancer; rather, that the information available and methods used simply do not allow any meaningful conclusions to be drawn. Recently a number of epidemiologists have published research which links occupational exposure to pesticides with cancer mortality in a number of countries but again it is difficult to draw meaningful conclusions from the work. No one knows exactly or even roughly what effect many pesticides have on human health at very low levels. One can only speculate.
One report found that brain cancer, central nervous system cancers, breast cancer, multiple myeloma, kidney cancer, non-Hodgkins lymphoma and melanoma were all increasing in people of 55 and older. Such trends remain unexplained but one might fairly speculate that a range of environmental factors could be involved.
In the light of our ignorance about the exact effects of pesticides on humans it would seem both wise and reasonable to allow consumers a right to basic information about possible residues in food or, as many pesticide residues are not monitored in many foods and as some pesticides still cannot be tested for, the right to know what pesticides have been applied to the food crops that they may wish to eat.
The effect of pesticide residues on wildlife has received a great deal of attention The problems of persistent organochlorine exposure for birds and marine life has been documented in detail and highlighted the inability of scientists to forecast the chronic effects of pesticides at extremely low levels in the environment. These residues have built up through the food chain with disastrous consequences for birds of prey. Problems have emerged for fish, shellfish and coral exposed to extremely low doses of pesticides in their environment either due to run-off or spray drift or spillage.