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Pesticide Classes and Exposure Hazards

Most pesticides contain an active ingredient or agent, synergists, solvents for dispersion and stabilization and adjuvants. Synergists enhance the killing power of the chemical agent. Adjuvants are additional additives, which may give many pesticides their competitive edge depending on their use application. Examples of adjuvants are spreaders and stickers which promote adhesion to plants, emulsifiers which act as detergents to stabilize water-oil interactions, penetrants which disperse the chemical agent from the surface to tissues, safeners as a component of fertilizers with pesticides to limit undesirable reactions, and anti-caking agents to prevent caking and clogging of dust-type pesticides in dispersion equipment. Most adjuvants have no toxicity effects.

The following is a list of commercially available pesticides, grouped by the class of pesticide based on active ingredient:

Common Uses and Health Hazards from Exposure

Pyrethroids (and Pyrethrins)
These compounds are insecticides, widely used to kill mosquitoes. Pyrethroids are a synthetic version of the plant pyrethrum, which is produced by chrysanthemum flowers. There are over 1,000 pyrethroids but only a small few are approved for use in the US: Permethrin (Biomist®), resmethrim (Scourge®) and Sumithrin (Anvil®). They are most commonly supplied as an ultra low-volume spray. The US EPA has tested these compounds extensively and found little risk to human health when applied properly. Exposure to these compounds at low levels may affect the respiratory system. Exposure at high levels, particularly to workers who spray these compounds may experience dizziness, headache, nausea, and diarrhea.

These compounds are widely used as insecticides and also as nerve agents acting on the enzyme acetylcholinesterase. Organophosphate pesticides degrade rapidly by hydrolysis on exposure to sunlight, air, and soil, although small amounts can be detected in food and drinking water. They are highly toxic to people exposed in large amounts. Symptoms of mild organophosphate exposure may include the following: runny nose, chest tightness, shortness of breath, sweating, nausea, vomiting, stomach cramps, muscle twitching and confusion. Severe exposure can lead to seizures, paralysis or coma; even death.

Organochlorines as insecticides were banned in the US in the 1980’s and 1990’s due to their highly toxic effects and their ability to stay in the environment (many are not water soluble) as a result they are considered POP or persistent organic pollutants. They tend to build up in fatty tissues and remain in our bodies for a long time (bioaccumulation). The most widely known organochlorines are DDT, aldrin, and endrin used in the 1940’s to control pests in agricultural crops. Today, lindane, endosulfan, methoxychlor, dicofol and pentachlorophenol are still registered for use. Organochlorines contribute to many acute and chronic illnesses. Symptoms of acute poisoning can include tremors, headache, dermal irritation, respiratory problems, dizziness, nausea, and seizures.

Organochlorines are also associated with many chronic diseases such as cancer, Parkinson’s disease, birth defects, respiratory illness and immune system suppression. Many are known or suspected hormone disruptors, and recent studies show that extremely low levels of exposure in the womb can cause irreversible damage to the reproductive and immune systems of the developing fetus.

Carbamates and Organonitrogen Pesticides
Like organophosphates, Carbamates and Organonitrogen insecticides such as Aldicarb, act on the enzyme cholinesterase. Exposure to high amounts of these compounds can cause weakness, blurred vision, headache, nausea, tearing, sweating, and tremors in humans. Very high doses can be fatal because it can paralyze the respiratory system.

Solvents in Pesticides
Solvents act as vehicles to dispense the chemical agents but also to stabilize it in solution. These vehicles are often proprietary information and not disclosed as public information unless in emergency situations. Commonly used solvents as pesticide vehicles are: BTEX, Petroleum distillates, alcohols, glycols, ethers, and chlorinated solvents.
For more information about sampling media and analysis products for BTEX, BTEX and other VOCs under air monitoring applications for the Petrochemical Industry.

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