EPA seeking comment on chlorpyrifos preliminary human health risk assessment

EPA is inviting comment on a preliminary human health risk assessment for the pesticide chlorpyrifos.  EPA's 2011 chlorpyrifos preliminary human health risk assessment is the most current scientific review to date.  It includes the results of extensive new research and the findings of a number of new studies that have become available since the agency's last human health risk assessment for chlorpyrifos, completed in June 2000. 

EPA is requesting comment and input on key areas in the preliminary risk assessment, including the appropriate FQPA safety factor to use in the final risk assessment, the limitations of assessing residential bystander inhalation exposure, the conversion of chlorpyrifos to the more toxic degradate chlorpyrifos oxon during drinking water treatment and distribution, and the impact of alternative drinking water treatment processes on chlorpyrifos and the oxon in finished drinking water.  As discussed in a Reader's Guide accompanying the preliminary risk assessment, such data and information will be useful to the agency in further refining and developing the final chlorpyrifos human health risk assessment.  In developing the final assessment, the agency will consider the weight of evidence of all available data, including animal and epidemiology data that just recently became available, as well as comments and new information received during the comment period on the preliminary risk assessment.

The preliminary risk assessment is part of EPA's registration review program that ensures all registered pesticides continue to meet current safety standards for registration; that is, they will not cause unreasonable adverse effects when used according to label directions and precautions. Issuing the chlorpyrifos preliminary human health risk assessment also fulfils a legal commitment in a December 2010 Stipulation and Order addressing a July 2010 lawsuit by the Natural Resources Defense Council (NRDC) and Pesticide Action Network North America (PANNA).  This lawsuit alleged that EPA had "unreasonably delayed" its response to their 2007 petition to revoke all tolerances and cancel all registrations for chlorpyrifos.  EPA plans to respond NRDC and PANNA's petition by the November 23, 2011, due date.