The federal government, in cooperation with the states, carefully regulates pesticides to ensure that they do not pose unreasonable risks to human health or the environment. As part of that effort, the U.S. Environmental Protection Agency (EPA) requires pesticide producers to provide extensive test data that demonstrate pesticide products can be used without posing harm to human health and the environment. EPA scientists and analysts carefully review these data to determine whether to register (license) a pesticide product or a use and whether specific restrictions are necessary.

More than 1,055 active ingredients are registered as pesticides, which are formulated into thousands of pesticide products that are available in the marketplace. EPA plays a critical role in evaluating these chemicals prior to registration and in reevaluating older pesticides already on the market, to ensure that they can be used with a reasonable certainty of no harm. The process EPA uses for evaluating the health impacts of a pesticide is called risk assessment.

EPA uses the National Research Council's four-step process for human-health risk assessment:

1. Hazard identification

2. Dose-response assessment

3. Exposure assessment

4. Risk characterization

Step One: Hazard Identification (Toxicology)

The first step in the risk-assessment process is to identify potential health effects that may occur from different types of pesticide exposure. EPA considers the full spectrum of a pesticide's potential health effects.

Generally, for human-health risk assessments, many toxicity studies are conducted on animals by pesticide companies in independent laboratories and evaluated for acceptability by EPA scientists. EPA evaluates pesticides for a wide range of adverse effects, from eye and skin irritation to cancer and birth defects in laboratory animals. EPA may also consult the public literature or other sources of supporting information on any aspect of the chemical.

Step Two: Dose-Response Assessment

Paracelsus, the Swiss physician and alchemist, the "father" of modern toxicology (1493–1541) said, "The dose makes the poison."

In other words, the amount of a substance a person is exposed to is as important as how toxic the chemical might be. For example, small doses of aspirin can be beneficial to people; but at very high doses, this common medicine can be deadly. In some individuals, even at very low doses, aspirin may be deadly.

Dose-response assessment involves considering the dose levels at which adverse effects were observed in test animals and using these dose levels to calculate an equal dose in humans.

Step Three: Exposure Assessment

People can be exposed to pesticides in three ways:

—Inhaling pesticides (inhalation exposure),

—Absorbing pesticides through the skin (dermal exposure), and

—Getting pesticides in their mouth or digestive tract (oral exposure).

Depending on the situation, pesticides could enter the body by any one or all of these routes.

Step Four: Risk Characterization

Risk characterization is the final step in assessing human health risks from pesticides. It is the process of combining the hazard, dose-response, and exposure assessments to describe the overall risk from a pesticide. It explains the assumptions used in assessing exposure, as well as the uncertainties that are built into the dose-response assessment. The strength of the overall database is considered, and broad conclusions are made. EPA's role is to evaluate both toxicity and exposure and to determine the risk associated with use of the pesticide.

Simply put,
RISK = TOXICITY x EXPOSURE.

This means that the risk to human health from pesticide exposure depends on both the toxicity of the pesticide and the likelihood of people coming into contact with it. At least some exposure and some toxicity are required to result in a risk. For example, if the pesticide is very poisonous but no people are exposed, there is no risk. Likewise, if there is ample exposure but the chemical is nontoxic, there is no risk. However, usually when pesticides are used, there is some toxicity and exposure, resulting in a potential risk.

EPA recognizes that effects vary between animals of different species and from person to person. To account for this variability, uncertainty factors are built into the risk assessment. These uncertainty factors create an additional margin of safety for protecting people who may be exposed to the pesticides. The Food Quality Protection Act (FQPA) requires EPA to use an extra tenfold safety factor, if necessary, to protect infants and children from effects of the pesticide.

EPA evaluates studies conducted over different periods of time and that measure specific types of effects. These tests are evaluated to screen for potential health effects in infants, children, and adults.

Acute testing: Short-term exposure; a single exposure (dose)

—Oral, dermal (skin), and inhalation exposure

—Eye irritation

—Skin irritation

—Skin sensitization

—Neurotoxicity

Subchronic testing: Intermediate exposure; repeated exposure over a longer period of time (that is, 30 to 90 days)

—Oral, dermal (skin), and inhalation

—Neurotoxicity (nerve system damage)

Chronic toxicity testing: Long-term exposure; repeated exposure lasting for most of the test animal's life span. This is intended to determine the effects of a pesticide after prolonged and repeated exposures.

—Chronic effects (non-cancer)

—Carcinogenicity (cancer)

Developmental and reproductive testing: Identify effects in the fetus of an exposed pregnant female (birth defects) and how pesticide exposure affects the ability of a test animal to successfully reproduce.

Mutagenicity testing: Assess a pesticide's potential to affect the cell's genetic components.

Hormone disruption: Measure effects for their potential to disrupt the endocrine system. The endocrine system consists of a set of glands and the hormones they produce that help guide the development, growth, reproduction, and behavior of animals, including humans.

Risk Management

Once EPA completes the risk-assessment process for a pesticide, this information is used to determine if (when used according to label directions), there is a reasonable certainty that the pesticide will not harm a person's health.

Using the conclusions of a risk assessment, EPA can then make a more informed decision regarding whether to approve a pesticide chemical or use, as proposed, or whether additional protective measures are necessary to limit occupational or nonoccupational exposure to a pesticide. For example, EPA may prohibit a pesticide from being used on certain crops because consuming too much food treated with the pesticide may result in an unacceptable risk to consumers. Another example of protective measures is requiring workers to wear personal protective equipment (PPE) such as a respirator or chemical-resistant gloves, or not allowing workers to enter treated crop fields until a specific period has passed.

If after considering all appropriate risk reduction measures, EPA finds that the pesticide still does not meet the agency's safety standard, it will not allow the proposed chemical or use. Regardless of the specific measures enforced, EPA's primary goal is to ensure that legal uses of the pesticide are protective of human health, especially the health of children, and the environment.

Federal law requires detailed evaluation of pesticides to protect human health and the environment. In 1996, Congress made significant changes to strengthen pesticide laws through the Food Quality Protection Act (FQPA). Many of these changes are key elements of the current risk-assessment process. FQPA required that EPA consider

1. A new safety standard: FQPA strengthened the safety standard that pesticides must meet before being approved for use. EPA must ensure with a reasonable certainty that no harm will result from the legal uses of the pesticide.

2. Exposure from all sources: In evaluating a pesticide, EPA must estimate the combined risk from that pesticide from all nonoccupational sources, such as food sources, drinking water sources, and residential sources. Residential sources include pesticide applications in and around the home made by the homeowner or a professional, such as the use of ant baits, wasp sprays, and weed and feed herbicides.

3. Cumulative risk: EPA is required to evaluate pesticides in light of similar toxic effects that different pesticides may share, or "a common mechanism of toxicity." At this time, EPA is developing a methodology for this type of assessment.

4. Special sensitivity of children to pesticides: EPA must ascertain whether there is an increased susceptibility from exposure to the pesticide to infants and children. EPA must build an additional tenfold safety factor into risk assessments to ensure the protection of infants and children unless it is determined that a lesser margin of safety will be safe for infants and children.

(Phil Nixon. Slightly modified from an EPA fact sheet available at http://www.epa.gov/pesticides/factsheets/riskassess.htm.)

Last year I wrote an article on disposal of household hazardous waste that included a schedule of collection events for the year. Due to popular demand, here is that information for 2008. What can you do with old or unwanted pesticides? One could suggest several things but here are your best, legal options:

1. Use them up. You can usually apply them to a labeled-use site regardless of whether or not pests are present. Be sure to read and follow all label directions. Sometimes pesticides are taken off the market, or certain uses are removed from the label. In those cases, existing stocks can typically still be used. Rarely does US–EPA order a stop-use on the product. For example, it is illegal to apply old stocks of chlordane or 2,4,5-T. To learn about the registration status of your product in question, you can contact the manufacturer or the Illinois Department of Agriculture, (217)785-2427.

2. Give them away. Fellow neighboring gardeners may be interested in your castoffs. It's not recommended that you sell unwanted pesticides. To sell a pesticide legally, if must still be in the original packaging with the complete label. If the pesticide is restricted use, you must be licensed in order to sell it. If the product registration has been cancelled, selling is illegal.

3. Take them to a hazardous waste collection event. The Illinois Environmental Protection Agency (IEPA) has scheduled 11 household hazardous waste (HHW) collection events to be held across Illinois this spring. (Click here for details.)

For a list of household hazardous waste materials that should be accepted at these events, please visit the Illinois Poison Center's Web site at http://www.mchc.org/ipc/AboutIPC/News/HouseholdWasteCollection.htm. If in doubt, it may be best to first contact the Waste Reduction Unit of the IEPA at (217)785-8604.

There are special hazardous material collection events for other nonhousehold types of pesticides:

• Agricultural pesticides are collected at various scheduled "Agricultural Pesticide Clean Sweep" events. Contact the Illinois Department of Agriculture, (217)785-2427, for more information.

• Structural pesticides (those used by professional applicators to control pests in and around structures) are collected at "Structural Pesticide Clean Sweep" sites. Contact the Illinois Department of Public Health, (217)782-4674, for more information.

(Michelle Wiesbrook)

Pesticides can move from the sites where they are applied into the surrounding environment through a number of ways, including spray drift and volatilization. EPA considers all pathways of exposure to ensure that all exposures are below levels of concern. Recently, EPA has begun to rethink how pesticides should be evaluated for inhalation exposure due to volatility.

Spray drift, or particle drift, can occur when pesticides move off the application site in the air as aerosols or particles (tiny spray droplets) during application or when the pesticides move that are attached to dust.

Volatilization occurs when pesticide surface residues change from a solid or liquid to a gas or vapor after an application of a pesticide has occurred. Once airborne, volatile pesticides can move long distances off site. Fumigant pesticides (used to treat soil before planting and to treat structures such as homes or storage bins) are especially volatile. But not all pesticides are volatile. Ones that have been known to cause vapor drift problems in the past include 2,4-D, dicamba, and clomazone herbicides. Ester formulations are particularly volatile.

Past practices for evaluating volatile pesticides. Historically, EPA has assessed inhalation exposures through volatilization for pesticides that have high vapor pressures (a characteristic that allows them to move easily into a gaseous state). Certain indoor-use pesticides and fumigants meet this high-vapor-pressure criterion. EPA has assessed exposures and risks related to volatilization for these pesticides in its reevaluation program for pesticides on the market, as well as during its registration program before allowing use. As a result, measures have been taken or are proposed to reduce exposures and risks below levels of concern.

New data lead to possible new evaluation methods. In addition to this re-evaluation work, EPA has reviewed data on volatilization that have recently become available from the Pesticide Action Network of North America (http://www.panna.org/drift/science), as well as many studies from the California Air Resources Board (http://www.cdpr.ca.gov/docs/emon/pubs/tac/diazinon.htm). EPA has been joined in this effort by the States of California, Florida, Minnesota, and Washington and by Canada. These data show that detectable exposures occur for semi-volatile pesticides. However, according to the EPA, the data available to date show that the exposures are low and generally below levels of concern. I am not a toxicologist and haven't studied the data intensely as EPA has, but I found the data featured at the above-mentioned web sites to be mildly alarming.

What EPA is doing. As a result of this analysis, EPA is in the process of reconsidering the criteria it uses to trigger an assessment of exposure from inhalation of pesticides that volatilize. In addition to high vapor pressure, other factors to consider are temperature, solvents and formulation type, size of area treated, and application method. This work will help to determine the best way to evaluate exposures resulting from volatilization and improve the risk assessment process. The agency continues to work with states and other federal agencies, as well as seeking input from our stakeholders to determine the most appropriate way to evaluate the significance of these exposures.

For more information. If you are interested in more details on how EPA evaluates pesticides to protect your health and environment, see

How EPA assesses health risks from pesticides (http://www.epa.gov/pesticides/
factsheets/riskassess.htm)

The reevaluation of pesticides (http://www.epa.gov/oppsrrd1/reevaluation/index.htm)

(Adapted by Michelle Wiesbrook from an EPA fact sheet at http://www.epa.gov/pesticides/about/intheworks/volatilization.htm.)

Table available as a PDF only.