Department of Health
P
O Box 2448
March
18, 2002
Dr.
Lynton S. Land
Post
Office Box 539
Ophelia,
Virginia 22530
Dear
Dr. Land:
Thank you for your recent letter regarding
the potential impacts that birds foraging on biosolids may have on shellfish
growing waters. I appreciate your concern for the quality and safety of the
Commonwealth's shellfish resources, and can assure you that the Virginia
Department of Health is committed to the preservation of a safe, high quality
shellfish resource.
As you stated in your letter, birds,
like virtually all warm-blooded animals, have the potential to contribute to
coliform contamination of waterways. This potential is certainly documented in
the literature regardless of the nature of their feeding habits. The relative
importance of birds as a source of contamination compared to other animals
however is a matter of debate. In spite of the fact that birds may often
defecate directly in the water, our staff as well as staff from the Maryland
shellfish sanitation program have looked at water samples that were taken in
the presence of large flocks of geese and not found elevated levels of fecal
coliform in the water. Further, the article you refer to entitled
"Coliform Contamination of a Coastal Embayment: Sources and Transport
Pathways" (Environmental Science and Technology, 1996, V30, p. 1872-1881),
also found that "While direct waterfowl inputs constitute a large potential
source of FC to Buttermilk Bay waters, sampling did not support a direct
relationship between this input and bay water column densities."
Additionally, due to the relatively small total volumes of fecal material
contributed by each bird, and the extensive dilution and dispersion of the
material once in a waterway, the cumulative affect on the bacteriological
quality of the water body is minimal except in shallow headwaters with low
tidal flushing with extensive bird fecal deposition.
In spite of the degree to which any
particular animal may contribute to the contamination of a shellfish growing
area, the National Shellfish Sanitation Program (NSSP) acknowledges that
contamination of a shellfish growing area from these sources has the potential
to affect the safety of shellfish harvested from the area. As a result, the
NSSP has established strict water quality standards for shellfish growing areas
to which all of the shellfish producing states in the United States as well as
a number of foreign countries adhere. The Division of Shellfish Sanitation
examines samples of water from our shellfish growing areas monthly to determine
if any of a multitude of these potential sources of fecal contamination exists
in an area; and, as required by the NSSP, will impose harvest restrictions on
any area that fails to meet these standards. Currently, there are over 200
shellfish area closures in Virginia. Although your letter stated that
"there are very few counties in Virginia where the Division of Shellfish
Sanitation imposes harvesting restrictions and where permits for the land
application of sewage sludge are granted", the fact is that these closures
are distributed across virtually every county that has a watershed draining
directly to a shellfish growing area, including those where permits for the
land application of sewage sludge have been granted.
The U.S
Environmental Protection Agency (EPA) has defined waters that are closed to the
harvest of shellfish as impaired. This designation is independent of the
specific source or sources of the contamination that is the cause for the
closure, which is rarely known. The Virginia Department of Health is, however,
currently working with the EPA and a number of Virginia state agencies and
academic institutions to determine the sources of contamination to these areas
and to establish a Total Maximum Daily Load (TMDL) for each of these areas as
required by the EPA. This work will be difficult and time consuming, but we
hope to learn a great deal from this process and certainly hope to reclaim some
shellfish area acreage that is currently closed as a result.
Birds are a
natural part of the landscape around Virginia's waterways, and some species
certainly are known to naturally feed in pastures, feedlots, and other areas
where coliform concentrations are high. Although birds do have the potential to
contribute to the bacterial contamination of a water body, there is no evidence
to support that foraging in a field where biosolids have been applied increases
the role that they may play in water body contamination over other foraging
sites. Regardless of the source, if a shellfish growing area is found to be
receiving coliform contamination that causes it to exceed the NSSP water
quality standards, these waters are closed to the harvest of shellfish thus
providing public health protection to the citizens of the Commonwealth and to
shellfish consumers.
Should you desire
further information, please contact Robert E. Croonenberghs, Director, Division
of Shellfish Sanitation or C. M. Sawyer, Director, Division of Wastewater
Engineering, Virginia Department of Health, 1500 East Main Street, Room 109,
Richmond, Virginia 23219 by telephone at (804) 786-5567, or by email:
Sincerely,
Robert
B. Stroube, M.D., M.P.H.
c: Govern Mark R.
Warner
Secretary Jane H.
Woods