UNITED STATES ENVIRONMENTAL PROTECTION AGENCY WASHINGTON D.C., 20460

MEMORANDUM September 3, 2014 PC Code: 109709
DP Barcode: 422414

SUBJECT: Response to Public Comments on the Preliminary Ecological Risk Assessment for
Metofluthrin.

TO: Veronica Dutch, Chemical Review Manager Risk Management and Implementation Branch 5
Pesticide Re-evaluation Division (7508P)

THROUGH: Dana Spatz, Branch

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### ..........,~-... Environmental Risk

## Bra~~**~ ~**  Environmental Fate and Effects Division (7507P)

FROM: 

# ¥ ov"" Melissa Panger, Ph.D

. , Senior

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### "\: James Wolf, Ph.D., Environmental Scientist ()tAAt')tuK**iA)~** Environmental Risk Branch 3 

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- ..... Environmental Fate and Effects Division (7507P)

The Metofluthrin Preliminary Work Plan (PWP) dated June 21,2013, and published in docket
number EPA-HQ-OPP-2012-0105 summarized the preliminary conclusions made in the April 16, 2013 ecological risk assessment and endangered species effects determination

. For all currently registered outdoor uses of metofluthrin (PC code 1 09709), metofluthrin is released into
the air as a vapor through passive dissipation, heat-driven or fan-driven evaporation. The ecological risk assessment conducted for the PWP for metofluthrin addressed potential risks
associated with deck strips**(~200** mg a.i./strip), personal fans**(~15** mg a.i./device), and candles**(~200** mg a.i./device)]. Following the PWP, a new use was proposed and assessed for a tabletop
mister (up to**~726** mg a.i./device). All ofthe currently registered outdoor use products containing metofluthrin are used to repel mosquitos in outdoor areas (e.g., backyards, patios, decks, and campsites). In the assessments for the currently registered outdoor uses, risks to aquatic and terrestrial organisms were not expected. There is also an indoor registered use for
metofluthrin to control bedbugs. An ecological risk assessment for the indoor bedbug use has2 not been conducted due to the expected limited e xposure to non-target wildlife and plants from this use (see below for details).

The Preliminary Work Plan requested public comment on the ecological risk assessment / endangered species effects determination. Commen ts were received from the San Francisco Bay Regional Water Quality Control Board (SFBRWQ CB) (8/26/2013), the Central Valley Regional Water Quality Control Board (8/26/2013), and th e California Stormwater Quality Association (CASQA) (8/23/2013). These comments were revi ewed by the Environmental Fate and Effects Division (EFED) and responses to the commen ts were provided on November 18, 2013. Since EFED’s latest response to comments, additi onal comments on the metofluthrin registration review have been received, in cluding additional comm ents from the CASQA (8/4/2014) and the SFBRWQCB (August 1, 2014), submitted during comment period for proposed interim decision. The most recent comments from CASQA and the SFBRWQCB are very similar to the comments submitted by these groups earlier in the registra tion review comment period. No new data or analyses were provided in the most recent comments received. The primary concerns related to the ecological risk assessment are:

1. The environmental risk assessment should consid er that some fraction of the mist will deposit on outdoor surfaces where it can then be transported to storm drains or directly to
water bodies.

2. The outdoor misters and indoor be dbug treatments are likely to cause and/or add to the pyrethroid toxicity in urban waterways.

3. Environmentally significant am ounts of metofluthrin will be released to indoor drains during washing of linens that have covered treated mattresses and of clothes worn by people using the mister and the clip-on vaporizer.

4. Aquatic toxicity data fo r known sensitive species, i .e., Hyalella Azteca

, Americamysis
bahia

, Chironomus dilutes , and Leptocheirus plumulosus should be required and incorporated into the risk assessment.

The potential for risk to non-ta rget organisms from pesticide exposure depends on many factors, most notably the toxicity of the chemical, its fate properties, its use patt ern(s), and its expected concentration(s) after use. Specific chemicals, ev en within the same class of chemicals, can vary dramatically from each other in respect to thes e factors. One fate parameter that varies significantly among pesticides within the pyrethr oid chemical class is photostability. First generation and Type 1 synthetic pyrethroids te nd to be much less photostable than Type 2 pyrethroids. For example, less photostable pyret hroids (like metofluthr in) can break down in sunlight with half-lives of an hour to hours, while more photostable pyrethroids can have3 photolysis half-lives in the tens (and sometime hundreds) of days (Spur lock and Lee 2008). This has impacts on their use patterns – for exam ple, the less photostable pyrethroids, like metofluthrin, are not used in agriculture. After reviewing the new comments received and reconsidering the specific toxicity profile for metofluthrin, its specifi c fate properties, its currently registered uses (both indoor a nd outdoor), and its expected environmental concentrations, EFED still feels that the risk s to nontarget organisms from the use of metofluthrin are low. Responses to the speci fic concerns received are provided below:

1. The environmental risk assessment should co nsider that some fraction of the mist will deposit on outdoor surfaces where it can then be transported to storm drains or directly to water bodies.

The review conducted by EFED for the metofluthrin mister use did consider the potential for the deposition of metofluthrin on outdoor surfaces an d its runoff to offsite water bodies (although it was not specifically modeled). The metofluthrin misters are small, tabletop misters (they are not the large, perimeter misters registered for some other pyrethroids). The misters contain a small percentage of metofluthrin ( i.e ., 0.23%) and each product contains at most 726 mg (0.0016 lb) of metofluthrin. Because the product is designed to k eep the metofluthrin suspended in air (that is the only way it is efficacious against adult mosquitoes) and is designed not to release the product all at once (the product mists peri odically over a severa l hour period), and be cause metofluthrin in air has a short half-life (<2 hr s.), only a small fraction of the applied metofluthrin is expected to deposit on outdoor surfaces. This combined w ith the limited use area, m eans that very little metofluthrin will be available for offsite transport from the mister use.

2. The outdoor misters and indoor bedbug treatm ents are likely to cause and/or add to the pyrethroid toxicity in urban waterways

.

As discussed above, EFED does not agree that the outdoor mister use will cause pyrethroid toxicity in urban streams because of the low envi ronmental exposure expected with this use (see above).

Regarding the registered products for the indoo r bedbug use, these products (which contain either 0.1 or 0.01% metofluthrin) can be spraye d on mattresses but cannot be sprayed directly onto bed linens (linens must be removed prior to the metofluthr in application). EFED does not typically conduct down-the-drain analyses for tr eated mattresses because of the limited exposure expected on linens. In the case of the metoflut hrin bedbug use, EFED agrees that a down-thedrain analysis for the indoor , bedbug use is not warranted. EFED concludes that the concentration in urban waterways is expected to be minimal based on the low amount of metofluthrin applied to mattresses (0.00086 lb metofluthrin can be applied per 1,000 ft 2 ), the limited amount of metofluthrin expected to transfer from the mattress to the linens, and the4 fraction of metofluthrin that is expected to persist and be available on the linens at the time of washing. Therefore, EFED does not agree that the indoor bedbug use will cause pyrethroid toxicity in urban streams because of th e low exposure expected with this use.

3. Environmentally significant amounts of metofluthrin will be released to indoor drains during washing of linens that have covered treated mattresses and of clothes worn by people using the mister and the clip-on vaporizer.

As discussed above, EFED does not agree th at environmentally significant amounts of
metofluthrin will be released to indoor drains during the washing of linens that have covered treated mattresses (see above).

Additionally, EFED does not agree that environmentally significan t amounts of metofluthrin will
be released to indoor drains dur ing the washing of clothes worn by people using the mister and clip-on vaporizer. Again, EFED does not typi cally conduct a down-the-drain analysis for the washing of clothes not directly treated or impre gnated with a pesticide du e to the expectation of limited exposure potential. In the case of the mister and clip-on fan uses, only a small fraction of
the metofluthrin released from the mister/fan is expected to persist on any surface (including clothes) after use – see above fo r the mister and the 2013 ecologica l risk assessmen t for the clipon fan use. Therefore, the amount of metofluthr in on clothing (if any) available for wash-off after the mister or fan use is expected to be minimal.

4. Aquatic toxicity data for known sensitive species, i .e., Hyalella Azteca , Americamysis
bahia , Chironomus dilutes , and Leptocheirus plumulosus should be required and incorporated into the risk assessment.

Risk assessment involves a consideration of bot h hazard (toxicity) and exposure. Therefore, even for toxic compounds, if limited or no exposure is expected, the potentia l for risk is low. Because the expected environmenta l aquatic concentrations for the currently registered uses of metofluthrin are expected to be low, additiona l toxicity data are not needed to make the ecological risk conclusions at this time. Howe ver, if the use pattern for metofluthrin was expanded or changed in a way that would resu lt in higher environmental concentrations, the request for additional toxicity data would need to be revisited.

REFERENCES :

Spurlock, F., and M. Lee (2008). Synthetic Pyrethroid Use Patterns, Properties, and
Environmental Effects. Synthetic Pyrethroids . ACS Symposium Series, Vol. 991. Pp. 3 – 25. Washington, DC.