1 Guide to Commenters - Chlorpyrifos Re vised Human Health Risk Assessment Docket # EPA-HQ-OPP-2008-0850

Publication Date: January 14, 2015

Purpose of This Guide to Commenters:

This guide is intended to assist commenters in providing input into the evaluation of human health effects from exposure to chlorpyrifos and any potential mitigation needed to address risk

concerns.

Summary and Questions The Environmental Protection Agency (EPA) is opening the public comment period for the Chlorpyrifos Revised Human Health Risk A ssessment (RHHRA). The public is invited to

comment on EPA’s RHHRA. Such comments and i nput could address, among other things, the Agency’s risk assessment methodologies and assump tions, as applied to this RHHRA, as well as possible mitigation for any risk as identified in the RHHRA. The Agency will carefully consider all comments, as well as any additiona l information or data provided in a timely manner, received during the public comment period and the responses to the questions presented below and any other information that is pr ovided will help in developing the proposed registration review decision on chlorpyrifos. The chlorpyrif os RHHRA, as well as all chlorpyrifos documents, can be found at www.regulations.gov , in docket EPA-HQ-OPP-2008- 0850. The public comment period will be for 60 days from the January 14, 2015 Federal Register Notice announcing the availability of the assessment.

This RHHRA shows some risks to workers who mix, load and apply chlorpyrifos pesticide products. A screening level drinking water analys is conducted as part of the RHHRA also shows that some chlorpyrifos use scenarios can lead to chlorpyrifos oxon concentrations in drinking water that pose exposure concerns from vulnerabl e watersheds in certain parts of the country. Factors including chlorpyrifos use, soil types, weather, and water treatment practices will influence drinking water exposure. Additional an alyses are needed in order to pinpoint the community water systems where concentrations may be of concern. This RHHRA shows no additional risks from chlorpyrifos exposures in food or exposures to bystanders and workers from airborne chlorpyrifos.

During this public comment period, stakeholders ar e specifically asked to provide information and data on the following questions that will assist EPA in de veloping the proposed registration review decision for human health for chlorpyrifos uses.

Areas of Focus for Questions Regarding the Revised Human Health Assessment

1. Occupational post-application exposures and risks were assessed for any crops where hand labor is anticipated following applicati ons of chlorpyrifos. Chlorpyrifos parent compound is the residue of concern for occ upational post-applica tion exposures that occur outdoors; however, it may be possible th at the formation of chlorpyrifos oxon is greater and its degradation slower in greenhouses when compared to the outdoor environment. Available exposure data indica te chlorpyrifos oxon may form in indoor2 environments [J.L. Martinez Vidal, et al. ( 1998)]. In order to account for the potential formation of chlorpyrifos oxon in greenhouses, risks were estimated for worker reentry into treated greenhouses for the parent ch lorpyrifos plus chlorpyrifos oxon using a conservative, total toxic residue approach.

In the 2011 preliminary HHRA, additional stud ies to address the unc ertainties regarding the formation and degradation of chlorpyrif os oxon in greenhouses were recommended.

To date, no data have been submitted.

We are seeking comment/input regarding the potential formation assessment of chlorpyrifos oxon in greenhouses including: a) whether commenters possess additional exposure data relating to the formation of chlorpyrifos oxon in greenhouses, b) the agency’s decision to assess chlorpyrifos oxon in greenhouses, or c) the methods used to assess worker reentry exposure to chlorpyrifos oxon in green houses (i.e., the total toxic residue approach).

2. In January 2013, a preliminary assessment of the potential risks from chlorpyrifos

volatilization was conducted. However, th is assessment was revised in June 2014 following submission of two vapor phase, inhalation toxicity studies by Dow AgroSciences which indicated no adverse effects occurred even at the saturation concentration for chlorpyrifos and chlorpyrifos oxon. Because these new studies demonstrated that no toxicity occurred even at the saturation concentration, which is the highest physically achievable concentration, there are no anticipated risks of concern from exposure to the volatilization of e ither chlorpyrifos or chlorpyrifos oxon.

We are seeking comment regarding the determ ination of no risks of concern anticipated from volatilization exposures of either chlorpyrifos or chlorpyrifos oxon.

3. The Agency has used a physiologically-b ased pharmacokinetic-pharmacodynamic model (PBPK-PD) to estimate points of de parture (PoDs) for 10% red blood cell acetylcholinesterase/cholinesterase (AChE/Ch E) inhibition following acute (single day, 24 hours) and steady state (21-day) exposures for a variety of exposure scenarios for chlorpyrifos and/or chlorpyrifos oxon. The use of the PBPK-PD model alleviates the need for the application of the in ter-species extra polation factor ( i.e. , animal to human extrapolation). Moreover, the agency has used the PBPK-PD model to determine DataDerived Extrapolation Factors relevant for a ssessing potential variab ility in sensitivity across the human population for infants, child ren, and non-pregnant adults. For women of childbearing age, the agency is applying the standard 10X intra- species extrapolation

factor since the PBPK-PD model cannot acc ount for variability in physiology during

pregnancy.

We are seeking comment regarding use of the PBPK-PD model to determine the appropriate extrapolation factors in the RHHRA.

4. Separate PoDs have been calculated for diet ary (food, drinking wate r), residential, and occupational exposures by varying inputs on types of exposures and populations exposed.3 Examples of inputs include: duration; rout e (dermal, oral, inhalation); body weights which vary by lifestage; exposure duration ( hours per day, days per week); and exposure frequency [events per da y (eating, drinking)].

We are seeking comment regarding the exposur e inputs used for the derivation of PoDs using the PBPK-PD model for each of the exposure scenarios considered in the RHHRA.

5. The agency has conducted a weight of ev idence analysis inte grating data from

mechanistic studies, animal behavior studi es, epidemiology, and a dose reconstruction analysis. Given the totality of the evidence, the agency concludes that chlorpyrifos likely played a role in the neurodevelopmental ou tcomes reported by the Columbia University investigators but uncertainties such as the lack of an established mode of action/adverse outcome pathway (MOA/AOP) for neurodevelopmental effects and the exposure to multiple AChE-inhibiting pesticides precludes definitive causal inference. However, there is sufficient uncertainty in th e human dose-response relationship for neurodevelopmental effects which prevents the agency from reducing or removing the statutory 10X Food Quality Protection Act (FQPA) Safety Factor. The FQPA 10X Safety Factor will be retained for infants, children, youths, and women of childbearing age for all exposure scenarios.

We are seeking comment on the RHHRA’s c onclusions regarding retaining the 10X FQPA Safety Factor to acc ount for the uncertainties re lated to neurodevelopmental outcomes observed in the chlorpyrifos database.

Questions regarding drinking water assessment

6. The drinking water assessment presents an approach for identifying individual watersheds and community water systems with high ( i.e. , drinking water concentrations greater than the drinking wate r level of concern (DWLOC) e xposure of chlorpyrifos and chlorpyrifos oxon. What uncerta inties and assumptions shou ld be considered or are

introduced when a watershed scale assessment approach is utilized as opposed to a national or regional scale assessment?

7. If you are aware of any regional, state, c ounty, and/or local surface water/drinking water monitoring data for chlorpyr ifos and the oxon, that were not considered in EPA’s assessment, please provide those data to us.

8. Based on empirical data that examined the formation and decline of chlorpyrifos oxon under simulated drinking water conditions [ i.e. , chlorination (the pr imary disinfection process used by community drinking water treatment systems], the drinking water assessment considers that all the chlorpyrifos in source surface water is converted to the oxon during the drinking water treatment pr ocess and distribute d to end users.

We are seeking comment or any informa tion on the decline of chlorpyrifos and

formation/decline of chlor pyrifos oxon under other drinki ng water treatment conditions or combinations of drinking water treatment conditions.4 Questions regarding additional info rmation on chlorpyrifos use

1. The agency conducted the occupational and residential exposure assessments and the drinking water assessment based on use of a master use summary document. The detailed information on application rates and use patter ns is the basis for these assessments. In order to clarify of chlorpyrif os usage, the agency obtained input from the chlorpyrifos registrants to compile the master use summary document to be reflective of the use profile of all active product labels. The document, among other information, presents all registered uses of chlorpyrifos and corre sponding maximum single application rates, equipment types, re-entry intervals (REIs), etc.

We are seeking comment as to a) whet her the master use summary document is accurately reflective of current chlorpyrifos labeling and b) whether the occupational and residential exposures and drinking water assessment are representative of current chlorpyrifos labeling.

2. If you are a grower, what is the lowest applica tion rate of chlorpyrifos (in either formulated lb/acre or active ingredient lb/acre) that is feasible for management of critical pests in your fields? Please pr ovide as much detail as possi ble (specific pests involved, reasons why the rate is the minimum useful one, etc.).

3. If you are a grower, what is th e minimum number of applicat ions per year that you would

consider feasible for effective use of chlorpyrifos in your crop, and why?

4. If you are a grower, please comment on what tim e of year you typically use chlorpyrifos, and what the time range of any such applications may be.

5. If you are a grower, please provi de information regarding acr es treated per application per day ( i.e. , field size treated per day), speci fic to your growing region and pest

spectrum

6. If you are a grower, please comment on what application methods you most frequently/typically use?

7. If you are a grower, please comment on what fo rmulation types you most frequently use?

8. If you are a grower, please comment on the app lication timing (date of first application and application intervals) by crop – national, state, and county? For example, when during the growing season do chlo rpyrifos applications predom inately occur in tree and vine crops?