Pesticide poisonings occur when chemicals intended to control a pest affect non-target organisms such as humans, wildlife, or bees. Since label directions required by the FIFRA are specifically designed to protect applicators and other humans, wildlife, and other environmental resources, the majority of pesticide poisonings result from violations of the label directions.
A major exception to the above rule of thumb, likely the worst single case of pesticide poisoning that has ever occurred, occurred due to an industrial accident at a Union Carbide pesticide manufacturing plant in Bhopal, India. On the night of December 3, 1984, a leak erupted from one of the tanks of methyl isocyanate, a gas that is an intermediate step in the production of carbaryl and aldicarb. For two hours the gas poured out and into the surrounding community, killing at least 3,800 people, and permanently disabling 40 people. About two thousand seven hundred people were partly disabled and over 400,000 have lingering health effects. The worst damage was to the eyes and lungs of the victims, but there were many other physical and psychiatric symptoms as well. One reason the accident was so severe was that all safety and backup systems were either disabled or inadequate.
The label is the key
Pesticides are designed to kill pests are usually toxic to other creatures as well, including the applicator, people working in the field, and non-target organisms such as birds, wild and domestic animals and bees (our primary pollinators). The label for each chemical pesticide is designed after extensive testing to maximize the effectiveness of this particular material and minimize risks. It often takes millions of dollars and several years to get a new material labeled ie approved for use, in the USA. Prevention of pesticide poisoning, as well as first aid response when accidents occur all should start with the label.
A fruit farmer in New York was preparing to use paraquat for weed control in his orchard. He spilled the concentrate on his bare forearm and hand, while mixing in the tank. He immediately flooded the affected skin with water from the filler hose. Notwithstanding his immediate washing, he died of chemical pneumonia the following week. His death was preventable had he not made three errors: 1. He had a casual attitude about a highly toxic chemical, 2. He was not wearing skin protection as directed by the label, and 3. He did not seek immediate medical attention after the accident.
Prior to using any pesticide, even the garden dust one buys at the discount store, one must carefully read the label. Knowing what it says may prevent injury or death. Pesticide labels are also legal documents. Using the material contrary to the directions is a violation; deliberate use in violation of the label is a crime.
There are three technical words used on pesticide labels that are important to check.
- Caution: mildly toxic, more than an ounce would be a lethal dose for a human (less for children).
- Warning more toxic, a teaspoon to a tablespoon is a lethal dose for an adult.
- Danger (accompanied by the symbol of the skull and crossbones), highly toxic - a minute amount can kill an adult.
Acute poisoning of humans
It is critical, when pesticide poisoning is suspected, to get competent treatment as rapidly as possible. Since pesticides have different modes of action and different medical responses, it is also necessary to refer to the label. If you are using a pesticide, be sure a copy of the label is present and accessible before you begin use. If you are rendering first aid, if at all possible, obtain a copy of the pesticide label for yourself and for the medical personnel.
If one is regularly using carbamate and organophosphate pesticides, it is important to obtain a baseline cholinesterase test. Cholinesterase is an important enzyme of the nervous system, and these chemical groups kill pests, and potentially injure or kill humans by inhibiting cholinesterase. If one has a baseline test, and suspects a poisoning, one can identify the extent of it by comparison of the current cholinesterase level with the baseline level.
- How poisonings occur
Pesticides can enter the body from inhalation, ingestion, or eye or skin contact. Many cases of poisoning occur to applicators without proper protection. Another scenario is that pesticides are directly applied to farmworkers in the field, or that they re-enter treated field before the toxicity levels drop to acceptable levels.
- First aid for poisoning victims
Never attempt to rescue someone or give mouth-to-mouth or mouth-to-nose rescucitation when an unknown or highly toxic substance is involved, you may become a victim yourself.
If ingested, do not induce vomiting and do not give excessive fluids. A small drink of water is fine, if the substance is irritating. If the substance is on the skin, wash thoroughly with water. If in the eye, flush with running water for at least 15 minutes. If inhaled, remove the person from the exposure to fresh air. If they are sleepy or having difficulty breathing put them in the recovery position (on their side, with their head lower than their body). Call your local Poison Control Center at 1-800-222-1222, or Emergency Service at 911 if the person has severe symptoms.
- Children more vulnerable than adults (placeholder)
- Symptoms of pesticide poisoning (placeholder)
Chronic poisoning, genetic damage, and birth defects of humans
Rachel Carson's Silent Spring brought about the first major wave of public concern over the chronic effects of pesticides. The organochlorine pesticides, like DDT, aldrin, and dieldrin are extremely persistent and accumulate in fatty tissue. Through the process of bioaccumulation (lower amounts in the environment get magnified sequentially up the food chain), large amounts of organochlorines can accumulate in top species like humans. There is substantial evidence to suggest that DDT, and its metabolite DDE, act as endocrine disruptors, interfering with hormonal function of estrogen, testosterone, and other steroid hormones.
Certain organophosphates have long been known to cause a delayed-onset toxicity to nerve cells, which is often irreversible. Several studies have shown persistent deficits in cognitive function in workers chronically exposed to pesticides (Jamal et al. 2000). Newer evidence suggests that these pesticides may cause developmental neurotoxicity at much lower doses and without depression of plasma cholinesterase levels.
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Poisoning of other non-target organisms (wildlife, bees)
An obvious side effect of using a chemical meant to kill is that one is likely to kill more than just the desired organism. Contact with a sprayed plant or "weed" can have an effect upon local wildlife, most notably insects.
Jamal GA, Hansen S, Julu PO. Low level exposures to organophosphorus esters may cause neurotoxicity. Toxicology. 2002 Dec 27;181-182:23-33. Review. PMID 12505280
- National Pesticide Information Center (NPIC) - Objective, science-based information about pesticide-related topics.
- Physician's Guide to Pesticide Poisoning
- Environmental Protection Agency - Recognition and Management of Pesticide Poisonings
- The Pollution in Newborns - From the Environmental Working Group
- Find Your Local Poison Control Center (Worldwide)
- WikiTox Information & Teaching material on human toxicologyko:농약 중독