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Reader’s Guide to the Pyrethrins/Pyrethroid Cumulative Risk Assessment

Docket # EPA-HQ-OPP-2011-0746

Publication Date: November 9, 2011

Purpose of this Reader’s Guide

The purpose of this note to reader is to provide an overview of the key information in 

EPA’s Pyrethrins/Pyrethroids Cumulative Risk Assessment and next steps associated 

with this group of chemicals. As noted, the Agency is requesting comment on this highly 

conservative cumulative assessment, including additional information or data that may be 

used to further refine the assessment.

Summary of the Cumulative Risk Assessment

• EPA’s recently completed cumulative risk assessment indicates that exposures

from the many current uses of pyrethrins and pyrethoid insecticides do not pose 

risk concerns for children or adults. 

• Further, there is ample room in the pyrethrins/pyrethroid cumulative “risk cup” to 

support consideration of new uses. 

• EPA therefore is issuing this final pyrethins/pyrethroid cumulative risk 

assessment and requesting comment, including information that may be used to 

further refine the assessment. 

• Once EPA completes and approves pyrethroid single chemical assessments, it is 

likely that new uses of these pesticides will be added, that may alleviate 

challenging new pest management situations such as the invasive stink bug and 

bed bugs. 

• EPA will update the individual pyrethrins and pyrethroid risk assessments as they 

come up for review. Endpoints for single chemicals may be different than those 

used in the cumulative assessment, since single chemical assessment endpoints 

are selected by analyzing the most sensitive effect observed in studies analyzing 

all body systems. By comparison, in evaluating the cumulative risk from 

pyrethroids, EPA has selected an endpoint that reflects the mode of action for this 

class of pesticides, specifically neurotoxicity.

• EPA’s screening level cumulative risk assessment considers all registered uses of 

pyrethrins/pyrethroids and includes exposure from food, drinking water and 

residential settings from the oral, dermal and inhalation routes of exposure. 

• The Agency considers this cumulative risk assessment to be highly conservative

because the assessment assumes that people are going to be exposed to the highest 

levels of residues in food, water, and in their homes all on the same day. For 

example, in estimating residential exposure, this screening level assessment 

assumed no dissipation of the chemicals, all individuals were exposed on the day 

of application, and exposure for each scenario occurred as a result of the 

pyrethroid with the highest risk estimate registered for that scenario. The 
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assessment also assumed co-occurrence of certain residential scenarios as worstcase situations. 

• The assessment shows that even if the highest levels of exposure were to occur, 

risk estimates for adults and children would be well below the Agency’s level of 

concern. 

• The Agency has also reevaluated the need for a 10X FQPA safety factor for 

human health risk assessments for pyrethroid pesticides. Based on information 

available in the database of pyrethroid guideline studies and in the open literature, 

EPA is reducing the safety factor to 1X for adults, including pregnant women. 

However, EPA is retaining a 3X for children based on age-dependent 

toxicokinetics. Details of this decision are captured in a separate document 

available in the docket, "Reevaluation of the FQPA Safety Factor for Pyrethroid 

Pesticides, D381210, June 27, 2011".

Current Status and Next Steps

While taking comment on the pyrethrins/pyrethroid cumulative risk assessment, EPA will 

begin to finalize the evaluation of pending pyrethroid registration actions and process 

new requests for registration. EPA is working with registrants individually on timelines 

for completing their respective actions. 

How to Submit Comments

EPA is providing an opportunity for interested parties to submit comments and input 

including any information or data that may be used to further refine the assessment. 

Submit comments identified by docket number EPA-HQ-OPP-2011-0746 no later than 

January 8, 2012, by one of the following methods. 

• Federal eRulemaking Portal, http://www.regulations.gov : Follow the on-line 

instructions for submitting comments. Mail: Office of Pesticide Programs (OPP), 

Regulatory Public Docket (7502P), Environmental Protection Agency, 1200 

Pennsylvania Avenue, NW, Washington, DC 20460-0001.

• Delivery: OPP Regulatory Public Docket (7502P), Environmental Protection 

Agency, Room S-4400, One Potomac Yard (South Building), 2777 S. Crystal 

Drive, Arlington, VA. Deliveries are accepted only during the Docket’s normal 

hours of operation (8:30 a.m. to 4:00 p.m., Monday through Friday, excluding 

legal holidays). Special arrangements should be made for deliveries of boxed 

information. The Docket telephone number is 703-305-5805. 

Related Information

The Pyrethrins/Pyrethroid Cumulative Risk Assessment and related documents are 

available in docket EPA-HQ-OPP-2011-0746 at Regulations.gov. The cumulative risk 

assessment is also available on the EPA Web page, Assessing Pesticide Cumulative 
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Risk/Common Mechanism Groups; Cumulative Exposure and Risk Assessment, 

http://epa.gov/pesticides/cumulative/common_mech_groups.htm.

Contact for Additional Information

Ms. Dana Friedman

Pesticide Re-evaluation Division (7508P)

Office of Pesticide Programs

Environmental Protection Agency

1200 Pennsylvania Ave., NW

Washington, DC 20460-0001

Telephone number: 703-349-5320

Fax number: 703-308-7070

Email address: friedman.dana@epa.gov