Pesticides

1. Pesticides

Most pesticides are poisonous and can be dangerous to the user, the environment, and the food consumer. Pesticides that reach the consumer generally do so by the oral route. Thus, stomach and bowel cancers are of particular interest to agronomic and agricultural scientists.

Pesticides may promote or induce cancer. Insecticides all are readily absorbed through the skin and may also be inhaled or ingested. Acute symptoms following massive exposure including vomiting; dizziness, tremors, and convulsions. Such exposure can be fatal. Other insecticides result in skin and lung irritation. Dithiocarbonates, a group of chemicals commonly used as fungicides, are highly irritating to the skin, eyes, and respiratory tract.

Tests for pesticides frequently establish the ability of the compounds to promote and induce cancer. A further complication is that of multiple carcinogens, a multiplier effect when one is added to another. The sale and use of some 2.000 pesticide products containing 23 potentially hazardous ingredients has been restricted by the EPA to farmers and commercial users.

1.1 Pronamide

This pesticide, used mainly on lettuce, alfalfa, and to a lesser extent, on berries, turf and sugar-beet seed, caused cancer in mice. On January 15, 1979 the FPA proposed that the continued use of pronamide be allowed, but with additional precautions lo reduce potential risks to humans. FPA Assistant Administrator Steven Jellinek said: “In general, EPA concluded that for all uses the economic benefits of pronamide outweigh its risks. Most pronamide is used on lettuce in California and Arizona, which produce most of this country’s lettuce. Without pronamide, the estimated loss to lettuce and alfalfa growers would be approximately $17.3 million annually. Pronamide is used primarily as an herbicide to control weeds, which compete with lettuce and alfalfa. Other herbicides available for weed control of these crops are not always as effective, and for lettuce these uses would result in additional labor costs for growers who would have to control the weeds by hand or mechanically.”

Organic gardeners will attest to the fact that highly poisonous sprays are not necessary to have a bumper crop of lettuce. A few weeds among the lettuce will do no harm but may distract or repel certain pests. There can never be any legitimate excuse for using sprays that are known to be harmful to the consumer. When weeds are controlled by hand or mechanically on a regular basis, they will not harm the crops and may in addition eliminate some unemployment .

1.2 Parathion

An organophosphorus pesticide, parathion was given in feed to rats and mice for 80 weeks. It was carcinogenic to the adrenal glands of male and female rats.

1.3 Nitrofen

Nitrofen is an agricultural pesticide used as a selective contact herbicide for pre- and post-emergent control of annual grasses and broad-leaf weeds on a variety of food crops. Agricultural workers and manufacturers are exposed through skin absorption and by inhalation. The general public is exposed through ingestion due to possible persistent residual quantities of nitrofen on food crops. Adverse effects on agricultural workers following excessive exposure over prolonged periods included a reduction of hemoglobin and white blood cell counts, inhibition of cholinesterase (an enzyme in the heart muscle) and abnormalities in red-blood and serum-enzyme levels. The chemical was given to rats and mice for 78 weeks. It proved to be a liver carcinogen in mice of both sexes and in female rats.

1.4 Maleic Hydrazide

Maleic hydrazide regulates the growth of unwanted “suckers” on about 90% of the United States tobacco crop and is also applied to 10 to 15% of domestic potatoes and onions to prevent sprouting after harvest. It is highly toxic to humans and has produced central nervous system disturbances and liver damage in experimental animals. It has led to liver and other tumors in some mice. It has resulted in genetic damage in plant and animal systems, a fact that often signals a cancer-causing effect.

1.5 ETU2-Imidazolidinethione

Cancer-causing ETU, a contaminant and breakdown product of some widely-used fungicides, can contaminate plants, whether sprayed onto leaves or mixed in the soil. Readily transmitted from roots to leaves, ETU persists for as long as two weeks. For this reason it is recommended that the fungicides called ethylenebisdithiocarbamates (EBDC), in use for 30 years, should not be applied to crops two weeks before harvest.

When ETU is given in large doses, it has been shown to be carcinogenic in rats, tumorigenic in mice, and teratogenic (fetus-deforming) in rats and mice. Reports have shown that cooked spinach contained more of the cancer-causing chemical than the corresponding raw spinach; an inadvertent addition to food of a carcinogen caused by the breakdown of remaining fungicide when heated. A heat-caused degradation product of widely-used EBDC fungicide, ETU is found 10 to 90 times higher in cooked tomatoes than in raw tomatoes. During cooking, the ETU presumably is formed from residues of the parent fungicides that are present on the food. The amount of ETU formed in the cooked produce varies with the parent fungicide and ultimately depends upon the amount of fungicide residue that remains on the harvested crops. Although the amount of ETU may drop to very low levels in 14 days, that is no reflection of the amount of this carcinogen that may be found in the cooked produce.

In addition, degradation products of unknown toxicity, for instance ethylene thiuram monosulfide, are formed from the EBDC fungicides in the field. Several toxicological studies have shown that ETU was carcinogenic in the thyroid of rats, tumorigenic in the liver of mice, and teratogenic in pregnant rats. Studies have also suggested an effect of ETU on the liver.

1.6 Dieldrin

Dieldrin is a neurotoxin (a toxin that destroys nerve tissue). First introduced by cotton growers in the 1950s, when the chemical was found to be more effective than aldrin, dieldrin has also been used as an insecticide on crops, for public health pest control, and for mothproofing woolen goods. The tests showed that there was a significant increase in the incidence of liver cancers in high-dose male rats and in cancer of the adrenal glands in low-dose female rats. Tumors occurred in the pituitary and thyroid glands in tests.

1.7 Chlorinated Hydrocarbons

Hydrocarbons in which one or more of the hydrogen atoms have been replaced by chlorine are called chlorinated hydrocarbons. Many members of the group have been shown to cause cancer in animals and some of them to cause cancer in humans. Among the designated carcinogens, chloroform, vinyl chlorides bis chloromethyl ether, trichlorethylene, aldrin, chlordane, dieldrin, heptachlor, lindane, methoxychlor, toxaphene, terpene polychlorinates, and carbon tetrachloride. Concern about the potential hazard of certain chlorinated hydrocarbons is based on their ubiquity; their persistence in the environment; their capacity to accumulate in living organisms, including humans and the human fetus; and the experimental evidence of a potential carcinogenic effect.

1.8 Chlordane

An organochlorine pesticide, chlordane was introduced in 1945 and was among the first to be developed for insect control. Because of its persistence in the environment, most of its uses were suspended by order of the EPA in 1975. Several specified uses are still permitted including pest control on pineapple, strawberries, and Florida citrus crops; it is also used for a number of other pest control problems.

Chlordane and heptachlor were once used at the rate of 14 to 16 million pounds per year. Current legal usage accounts for 6 to 8 million pounds per year. Chlordane causes cancer of the liver in mice. It is less toxic than other similar pesticides, but acute exposure has the effect of stimulating the central nervous system. It has also been implicated in acute blood abnormalities, such as aplastic anemia. It is said to be absorbed through the skin. It has been found to be mutagenic. Eventually, it will probably be banned entirely.

1.9 Atrazine

One of the most widely-used pesticides in the United States, atrazine reacts under acidic conditions such as those found in the stomach, to form a potential carcinogen. It is used as a weed-control agent for corn and for noncrop and industrial sites. Found in drinking water supplies in Iowa and Louisiana, atrazine reacts with nitrite to form N-nitrosoatrazine, a suspected carcinogen. Sodium nitrite is used as a meat preservative and may also be present in acid soils because of the large amounts of nitrite fertilizers used.

1.10 Amitraz

Amitraz is a pesticide used on pears in Washington, Utah, Oregon, Michigan, New York, and Pennsylvania since 1975 on an emergency basis to control an aphid-like insect called pear psylla. It is claimed that there is no effective alternative pesticide available to control the pear psylla, which is capable of damaging both the fruit and the trees. The EPA claims that without amitraz the economic losses to growers could be as high as $33 million for three years. On January 15, 1979, the EPA proposed to approve the pesticide on the condition that certain restrictions be imposed “to reduce potential risks to human health.” They said that amitraz could be used on pears for four years, pending completion of additional laboratory tests by the manufacturer. The proposal follows a full-scale review of the risk versus benefits of using the pesticide on pears. There is some evidence that it may cause tumors in laboratory animals and therefore might present “a small risk of cancer to humans.” As a result, EPA would require application only by trained users wearing protective clothing. To reduce residue levels on the fruit before it is marketed, EPA would require longer time periods from the time a crop is sprayed to the time it is harvested. Amitraz is distributed in this country by Upjohn of Kalamazoo, Michigan. It is estimated that about 120,000 pounds of it might be used on pears each year.

The facts still remain that this pesticide is extremely toxic and even in small doses are definitely harmful.