Pesticide Chlorpyrifos Risks to Workers, EPA Report

EPA is releasing an assessment for public comment on the potential for human health risk of the pesticide chlorpyrifos

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A pesticide used on corn and other U.S. crops poses health risks to workers who mix and apply it and also can contaminate drinking water, according to a new EPA report.

The US Environmental Protection Agency EPA is releasing an assessment of people’s risks from the pesticide chlorpyrifos for public comment. The assessment updates the June 2011 preliminary human health risk assessment based on new information including public comments. EPA factored in exposures from multiple sources and considered all populations in this revised assessment. The public comment period is expected to begin in mid-January, 2015 and will be open for 60 days.

What does EPA’s December 2014 human health risk assessment show?

This assessment shows some risks to workers who mix, load and apply chlorpyrifos pesticide products. When used in large amounts in small watersheds in certain geographic areas, chlorpyrifos also shows potential risks from drinking water. There were no additional risks from chlorpyrifos in food or exposure to bystanders and workers from airborne chlorpyrifos.

What are EPA’s next steps?

EPA is developing appropriate measures to ensure that workers that use or work around areas treated with chlorpyrifos are protected and that drinking water in vulnerable watersheds is protected.
As part of the ongoing registration review for chlorpyrifos, EPA is also assessing the ecological risks from chlorpyrifos in conjunction with the agency’s Endangered Species Protection Program; the results of the preliminary ecological risk assessment are expected later in 2015.

What is the registration status of chlorpyrifos?

Chlorpyrifos remains registered while it is undergoing registration review. Registration review ensures pesticides will not cause unreasonable adverse effects when used according to label directions and precautions and that there is a reasonable certainty of no harm from dietary and residential exposure. This revised human health risk assessment contributes to understanding how chlorpyrifos may affect humans, an important part of the registration review process.

How did EPA assess risks?

EPA assessed exposure from multiple sources including those from food, drinking water, pesticide inhalation and absorption of the pesticide through the skin for all populations, including infants, children and women of childbearing age. The assessment updates the June 2011 preliminary human health risk assessment based on new information received, including public comments and a new human response model.
This is one of the first risk assessments to employ a physiologically-based pharmacokinetic and pharmacodynamic (PBPK/PD) model. This is a mathematical model that enhances our ability to assess risk by allowing us to consider variations in a chemical’s effects on a person based on such variables as age and genetics and allows us to predict how the same dose may affect various members of a large population differently. EPA has held several meetings of the FIFRA Scientific Advisory Panels to get independent advice on the relevance and usefulness that a PBPK/PD model can provide in assessing a chemical’s risks and one specifically on PBPK/PD and chlorpyrifos.

Did EPA take into account the 10x safety factor specified under the Food Quality Protection Act to protect children?

Yes, EPA did retain the 10x factor for this risk assessment. EPA believes that the PBPK-PD model in conjunction with retention of the FQPA 10x safety factor is protective of children and other vulnerable populations.

Who is at risk for chlorpyrifos exposure?

We are concerned about some workers who mix, load and apply chlorpyrifos to agricultural and other non-residential sites. We are also concerned about workers who work around areas that are treated with chlorpyrifos, even if they are not using chlorpyrifos products as part of their jobs.

What would the signs or symptoms be for chlorpyrifos exposure?

At high enough doses chlorpyrifos can cause cholinesterase inhibition in humans; that is, it can impact the nervous system causing nausea, dizziness, confusion, and at very high exposures (e.g., accidents or major spills), respiratory paralysis and death. Anyone who exhibits these symptoms should seek immediate help from a local hospital, physician, or nearest poison control center.

Can chlorpyrifos affect wildlife?

Yes, and EPA has taken actions to help protect wildlife from chlorpyrifos exposure.
For example, many of the reported incidents of wildlife mortality associated with chlorpyrifos use were related to residential lawn and termite uses and use on golf courses. The residential uses have been eliminated, termiticide uses have been restricted, and the application rate on golf courses has been reduced. Additionally, no-spray buffers around surface water bodies, as well as rate reductions for agricultural uses further reduced the environmental burden of chlorpyrifos.
The agency is currently assessing the ecological risks for chlorpyrifos in conjunction with the agency’s Endangered Species Protection Program; the results of the preliminary ecological risk assessment are expected later in 2015.

What actions has EPA taken on chlorpyrifos?

The EPA has taken a number of actions that have limited the use of chlorpyrifos since 2000. These actions include:

  • In June 2000, the Agency eliminated all homeowner uses, except ant and roach baits in child resistant packaging.
  • In 2000, EPA required that all use of chlorpyrifos products in the United States be discontinued on tomatoes. The use on apple trees was restricted to pre-bloom and dormant applications. The grape tolerance was lowered to reflect the labeled dormant application.
  • In 2002, EPA restricted the use of chlorpyrifos on citrus and tree nuts as well other crops.
  • In 2012, EPA further limited the use of chlorpyrifos by significantly lowering pesticide application rates and creating “no-spray” buffer zones around public spaces, including recreational areas and homes.
Sources and more information
  • Revised Human Health Risk Assessment on Chlorpyrifos, EPA, January 5, 2015.
  • EPA Revised Chlorpyrifos Assessment Shows Risk to Workers,
    EPA press release, January 5, 2015.
  • EPA report finds pesticide poses risk to workers, spurs calls for ban, environmentalhealthnews, January 8, 2015.


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