MCPB TASK FORCE

C.M. Schofield, Technical Chairman

8325 Old Deer Trail

Raleigh, North Carolina  27615

Email: dgminc@bellsouth.net

December 2, 2008

Mr. James Parker

Special Review & Reregistration Division (7504P)

U.S. Environmental Protection Agency

Room S-4900, One Potomac Yard

2777 South Crystal Drive

Arlington, VA  22202-4501

RE:  MCPB Generic Data Call-In:  Status of Studies – Time Extension
Request

Dear James:

This letter pertains to the status of three studies required in the
generic data call-in (DCI) for MCPB:

Oyster acute toxicity study (Guideline 850.1025);

Acute fish toxicity test (Guideline 850.1075); and

Fish early-life stage toxicity test (Guideline 850.1400)

In March 2008 the three studies identified were granted a time extension
until December 7, 2008.  This letter is to advise you that the MCPB Task
Force will be able to meet the December 7, 2008 deadline for supplying
data to EPA to satisfy oyster acute toxicity (850.1025) data
requirements but will need additional time for acute fish toxicity
(850.1075) and fish early-life stage toxicity (850.1400) data
requirements.   

Initial study results for the acute fish toxicity test with sheepshead
minnow received from ABC Laboratories on 5 November 2008 demonstrated a
96-Hour NOEC of 35 mg a.e./L (acid equivalents/L) and a 96-Hour LC50 of
>35 mg a.e./L.  Upon receipt of the initial study results, we requested
that ABC conduct the study at higher concentrations in an attempt to
obtain a more accurate 96-Hour LC50 value.  The results of the repeat
study were received on 24 November 2008 and indicate 96-Hour NOEC and
96-Hour LC50 values of 47.1 and 62.2 mg a.e./L, respectively, based on
mean measured concentrations.  The draft report is in preparation but
will not be received until after the 7 December 2008 deadline.  While we
make every attempt to expedite review and finalization of the report, we
do not expect to be able to submit the final report until the end of
January 2009 and request an extension until that date.

The fish early-life stage toxicity test was contracted to Chemex
Environmental International Ltd in Cottenham, Cambridge UK.  The
laboratory has experienced repeated problems in obtaining eggs of
sufficient quality to conduct the study.  This has therefore resulted in
delay in initiation of the definitive study.  In our most recent
discussions with the laboratory they have indicated we should have a
draft report by February 2009.  Based on this schedule, we would expect
to finalize the study by the end of March 2009 with submission of the
final report in April.  We therefore request an extension until
mid-April 2009 for submission of the final report.

Should you have any questions or require any additional information,
please feel free to contact me at your convenience.

Sincerely,

C.M. Schofield

EPA Liaison, MCPB Task Force

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