Chemical Exposure An Overview

James E. Lessenger

Key words: pesticides, growth regulators, fertilizers, nutrients, buffers, petroleum products

Agricultural chemicals comprise thousands of formulations, including petroleum products, pesticides, growth regulators, buffers, nutrients and fertilizers, and veterinary medications. These chemicals may be used as solids in granular, powder, pellet, or block form; liquids in mists and sprays; or in gaseous forms as fumigants or fuels. Application of chemicals to crops may be by sprays of liquids from aircraft or ground machines; broadcast of solids from aircraft, vehicles, or stationary sources; injection of gas, liquid, or solids into water, soil, animals, or feed; or gaseous exposure in fumigation cells. Animals may be dipped in pools of dilute insecticides to remove surface insects. To save on manpower and fuel, it is common to apply five or more chemicals at once to a crop, making it difficult to determine which are the relevant agents. Mass casualty situations may result from the sudden release of large quantities of chemicals from a manufacturing, storage, or transportation facility, or from the group's perception of a release as in mass psychogenic hysteria (Table 13.1) (1-3).

Exposure does not necessarily equal poisoning. If a person is working in an area where a chemical is being used, he or she may not be exposed. Exposure to a chemical may not mean there will be enough external or internal contact to produce the physiological changes of poisoning. Poisoning may not produce a clinical level of illness, impairment, or disability. It is a mistake to assume a person has become ill from a chemical just because he or she was present in the vicinity where it was thought to have been used. It is important to consider the differential diagnoses of chemical illness when evaluating an alleged chemical injury for causation (1).

The massive amount of information and misinformation in the public media about farm chemicals complicates the evaluation of the patient. Some chemicals produce a particularly noxious odor that can cause nausea or anxiety about exposure, yet cause none of the physiological processes of poisoning. Dursban™, for example, has a particularly obnoxious odor, and small

Table 13.1. Farm chemicals, pesticides, and other chemical agents (1,2,16).

Farm chemicals


Gasoline fuels

Coumadin and other anticoagulants

Diesel fuels


Jet fuels

Sodium fluoroacetate

Oils and lubricants


Fluids (hydraulic, etc)


Kerosene (mixed with chemicals as


applied to crops to make the pesticides

Others, including sulfur, captan, captofol

settle on the leaves)

Antimicrobials (disinfectants)

Pesticides (Chapter 16)



Chlorine-releasing agents






Growth regulators (Chapter 15)


Plant regulators

Synthetic pyrethroids

Insect regulators


Buffers (to bring chemical mixtures to


neutral pH before application)

Microbiologicals (Bacillus

Nutrients and fertilizers (Chapter 14)


Elemental compounds

Elemental substances (sulfur)

Anhydrous ammonia





Urea derivatives

Veterinary medications






Hormones to promote growth

and production

Source: Data from Lessenger (1), O'Malley (2), Tordoir et al. (4), Reigart and Roberts (5).

Source: Data from Lessenger (1), O'Malley (2), Tordoir et al. (4), Reigart and Roberts (5).

amounts can cause anxiety and fear in people when no significant exposure has occurred. As urban growth encroaches upon farmland, more and more people live adjacent to farms and farm animals. Unpleasant odors familiar to those people working in agriculture may be misinterpreted by new arrivals as dangerous toxicants. A careful history and physical examination can differentiate fears and anxiety from actual poisoning (6,7).

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