Pesticides; Harmful Effects and Emergency Response

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Pesticides; Harmful Effects and Emergency Response – Most pesticides are designed to harm or kill pests. Because some pests have systems similar to the human system, some pesticides also can harm or kill humans. Fortunately, humans usually can avoid harmful effects by avoiding being exposed to pesticides.

Humans may be harmed by pesticides in two ways: they may be poisoned or injured. Pesticide poisoning is caused by pesticides that harm internal organs or other systems inside the body. Pesticide-related injuries usually are caused by pesticides that are external irritants.

Pesticides that are chemically similar to one another cause the same type of harmful effects to humans. These effects may be mild or severe, depending on the pesticide involved and the amount of overexposure. But the pattern of illness or injury caused by each chemical group is usually the same. Some pesticide chemical families can cause both external irritation injuries and internal poisoning illnesses.

Some pesticides are highly toxic to humans; only a few drops in the mouth or on the skin can cause extremely harmful effects. Other pesticides are less toxic, but too much exposure to them also will cause harmful effects. A good equation to remember is:

Hazard = Toxicity x Exposure

Hazard is the risk of harmful effects from pesticides. Hazard depends on both the toxicity of the pesticide and your exposure.

When a pesticide contacts a surface or organism, that contact is called a pesticide exposure. For humans, a pesticide exposure means getting pesticides in or on the body. The toxic effect of a pesticide exposure depends on how much pesticide is involved and how long it remains there.

Types of Exposures

Pesticides contact your body in four main ways:

  • Oral exposure (when you swallow a pesticide),
  • Inhalation exposure (when you breathe in a pesticide),
  • Ocular – (through the eyes), or
  • Dermal (through the skin)

Avoiding Exposure

Avoiding and reducing exposures to pesticides will reduce the harmful effects from pesticides. You can avoid exposures by using safety systems, such as closed systems and enclosed cabs, and you can reduce exposures by wearing appropriate personal protective equipment (PPE), washing exposed areas often, and keeping your personal protective equipment clean and in good operating condition.

In most pesticide handling situations, the skin is the part of the body that is most likely to receive exposure.

About 97 percent of all body exposure that happens during pesticide spraying is through skin contact.

The only time inhalation is a greater hazard than skin contact is when you are working in a poorly ventilated enclosed space and are using a fumigant or other pesticide that is highly toxic by inhalation.

The amount of pesticide absorbed through your skin (and eyes) and into your body depends on — the pesticide and the material used to dilute it.

ECs, oil-based liquid pesticides, and oil-based diluents (such as xylene) are, in general, absorbed most readily. Water-based pesticides and dilutions (such as WPs, SPs and DFs) usually are absorbed less readily than the oilbased liquid formulations but more readily than dry formulations. Dusts, granules, and other dry formulations are not absorbed as readily as liquids.

The area of the body exposed. The genital area tends to be the most absorptive. The scalp, ear canal, and forehead are also highly absorptive.

Cuts, abrasions, and skin rashes allow absorption more readily than intact skin. Hot, sweaty skin will absorb more pesticide than dry, cool skin.

Causes of Exposure

One of the best ways to avoid pesticide exposures is to avoid situations and practices where exposures commonly occur. Oral exposures often are caused by:not washing hands before eating, drinking, smoking, or chewing, mistaking the pesticide for food or drink, accidentally applying pesticides to food, or splashing pesticide into the mouth through carelessness or accident.

Inhalation exposures often are caused by: prolonged contact with pesticides in closed or poorly ventilated spaces, breathing vapors from fumigants and other toxic pesticides, breathing vapors, dust, or mist while handling pesticides without appropriate protective equipment, inhaling vapors immediately after a pesticide is applied; for example, from drift or from reentering the area too soon, and using a respirator that fits poorly or using an old or
inadequate filter, cartridge, or canister.

Dermal exposures often are caused by: not washing hands after handling pesticides or their containers, splashing or spraying pesticides on unprotected skin, wearing pesticide contaminated clothing (including boots and gloves), applying pesticides in windy weather, wearing inadequate personal protective equipment while handling pesticides, and touching pesticide-treated surfaces.

Eye exposures often are caused by splashing or spraying pesticides in eyes, applying pesticides in windy weather without eye protection, rubbing eyes or forehead with contaminated gloves or hands, and pouring dust, granule, or powder formulations without eye protection.


Toxicity is a measure of the ability of a chemical to cause harmful effects. It depends on the types and amounts of active ingredient(s), solvent(s), – – inert ingredient(s), and formulation. The toxicity of a particular pesticide is measured by subjecting laboratory animals (usually rats, mice, rabbits, and dogs) or tissue cultures to different dosages of the active ingredient and of the formulated product over various times.

These toxicity studies help to estimate the risk that the pesticide may cause harmful effects in humans.

However, some people react more severely or more mildly than estimated. Be alert to your body’s reaction to the pesticides you are handling. Some people seem to be especially sensitive to individual pesticides or to groups of similar pesticides.

You may have a choice of pesticides for a particular pest problem. Consider how toxic each pesticide is to persons who will use it or be exposed to it.

Harmful Effects
Pesticides can cause three types of harmful effects: acute, delayed, and allergic.

Acute Effects
Acute effects are illnesses or injuries that may appear immediately after exposure to a pesticide (usually within 24 hours).

Studying a pesticide’s relative ability to cause acute effects has been the main way to assess and compare how toxic pesticides are. Acute effects can be measured more accurately than delayed effects, and they are more easily diagnosed than effects that do not appear until long after the exposure. Acute effects usually are obvious and often are reversible if appropriate medical care is given promptly. (Source:

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