# Presentation: 110445

## Selenium Eco Risk Issues

**Ed Hanlon**
**U.S. EPA/ORD/OSP**
**Reagan Building**
**Washington DC  **
**hanlon.edward@epa.gov**

## Selenium Aquatic life criteria overview 

**	********	****EPA updated its national aquatic life criteria for ****	****	****selenium in 1987.  **
**	********	****EPA is currently working to revise national ****	****	****freshwater aquatic life criteria for selenium **
**	********	****1987 criteria can not be conveniently adjusted to ****	****	****account for combined toxicity of different selenium ****	****forms or other factors that might affect selenium ****	****bioavailability, mostly due to lack of appropriate ****	****data.  **
**	********	****New literature has accumulated on the toxicity of ****	****different forms of selenium to aquatic life. **

## EPA plans to publish two products from its selenium criteria revision effort 

**1) Revised freshwater acute and chronic Selenium criterion (i.e., criterion maximum concentration or CMC).**
**	********	**will build upon previous work conducted under Great 	Lakes Water Quality Initiative Guidance (61*Federal **	**Register *58444-58449) which addressed the combined 	toxicity of different selenium forms.
**	********	**final, peer reviewed acute and chronic criterion is 		expected to be complete by December 2001

## EPA plans to publish two products from its selenium criteria revision effort (cont’d)

**1) Guidelines for making site-specific adjustments to the chronic criterion  **
**	********	**The guidelines may be developed by reviewing 		nationally available tissue residue data, factoring in the 	bioaccumulation rates at the specific site of concern.
**	********	**The guidelines are very important because a single 		national criterion has been criticized.
**	********	**final, peer reviewed site-specific guidelines is expected 	to be complete sometime after publication of the acute 	and chronic criteria.

## Complex selenium biogeochemistry in the aquatic environment greatly complicates the derivation of aquatic life criteria

**	********	**Multiple oxidation states of selenium compounds exist 	in ambient surface waters (e.g., selenate (Se+6), selenite 	(Se+4), elemental selenium (Se0) and selenide (Se-2)), 	with each displaying different toxicological and 		chemical properties.
**	********	**Selenium can undergo biotransformation between its 	inorganic and organic forms which can affect its 		bioavailability and toxicity.
**	********	**Bioaccumulation of selenium in aquatic food webs 		complicates the derivation of aquatic life criteria 		because both water and dietary exposures need to be 	considered

## Report on the peer consultation workshop for Selenium Aquatic Toxicity and Bioaccumulation (EPA-822-R-98-007)

**	********	**released in September 1998 (EPA-822-R-98-007), 		available at http://www.epa.gov/ost/selenium
**	********	**peer consultation workshop held May 27-28, 1998 in 	Washington, D.C., involving experts in selenium 		aquatic toxicology, geochemistry, ecotoxicology, 		bioaccumulation, and biochemistry.
**	******** **	assessed state of the science on several technical issues 	related to selenium chronic toxicity and 			bioaccumulation in water, tissue, and sediment. **	**
**	********	**not a consensus building exercise; policy discussions 	not entertained.

## Generally, but not necessarily universally, accepted themes from peer consultation workshop (doesn’t necessarily reflect EPA views or policy) 

_**Water Issues**_
**	********	**Most toxicologically important forms of 			organoselenium dissolved in water are protein or 		peptide-bound forms; freely dissolved seleno- amino 	acids were considered less toxicologically important due 	to their extremely low occurrence in water
**	********	**Available data too sparse to support quantitative 		relationships between selenium chronic toxicity and 	water quality parameters.
**	********	**Extrapolation of acute toxicity/water quality 			relationships to chronic toxicity is highly uncertain.

## Generally, but not necessarily universally, accepted themes from peer consultation workshop (doesn’t necessarily reflect EPA views or policy)(continued) 

_**Tissue Issues**_
**	********	**Most toxicologically important forms of organoselenium are 		protein or peptide-bound forms, although most measurements have 	been made of total selenium.
**	********	**Reproductive tissues in fish (ovaries, eggs) are the most reliable 	tissue for correlating selenium tissue residues to chronic effects, 	although need additional residue-effects data.
**	********	**Poor correlation between water concentrations and tissue residues 	in higher trophic level aquatic organisms, due to many factors 		including varying patterns of historical loadings and temporal 		asynchrony between water and tissue concentrations.

## Generally, but not necessarily universally, accepted themes from peer consultation workshop (doesn’t necessarily reflect EPA views or policy)(continued)

_**Sediment Issues**_
**	********	**Sediments are the dominant sink for selenium in aquatic 	ecosystems and represent an important link and 		exposure source to the benthic driven food web.
**	********	**Elemental and organoselenium (in detritus) are 		dominant selenium forms in aquatic sediments, although 	most measurements have been made on total selenium.
**	********	**Sediment toxicity data base is very limited and does not 	support broad-based quantitative relationships between 	toxicity and sediment quality characteristics

## Generally, but not necessarily universally, accepted themes from peer consultation workshop (doesn’t necessarily reflect EPA views or policy)(continued)

_**Cross Cutting Issues**_
**	********	**Selenium residues in fish and sediments in freshwater 	ecosystems respond slowly to changes in selenium 		concentrations in water (on the order of months or 		years) while residues in lower trophic level organisms 	(plankton) respond rapidly (days)
**	********	**Type of water body (lentic vs. lotic) can have a large 	effect on selenium cycling. However, such water body 	types can be closely interconnected.

## Generally, but not necessarily universally, accepted themes from peer consultation workshop (doesn’t necessarily reflect EPA views or policy 

_**Water Issues**_
**	********	**Most toxicologically important forms of 			organoselenium dissolved in water are protein or 		peptide-bound forms; freely dissolved seleno- amino 	acids were considered less toxicologically important due 	to their extremely low occurrence in water
**	********	**Available data too sparse to support quantitative 		relationships between selenium chronic toxicity and 	water quality parameters.
**	********	**Extrapolation of acute toxicity/water quality 			relationships to chronic toxicity is highly uncertain.

## Recent Selenium References, some generated by EPA

**	********	**Selenium LC50 Calculations, Robert Pepin  312-886-1505
- 		Selenium Acute Criterion (Aquatic Life) Great Lakes, Keith 		Sappington  202-260-9898
**	********	**Selenium Effects in Streams; Study Reports on Selenium Effects in 	Experimental Streams, Keith Sappington 202-260-9898
**	********	**National Freshwater Acute Criteria for Selenium,  Keith 		Sappington 202-260-9898
**	********	**National Freshwater Chronic Aquatic Life for Selenium and Site 	Specific Criteria Guidelines, Keith Sappington, 202-260-9898
**	********	**References available to EPA for developing or revising aquatic life 	criteria for Selenium. 						http://www.epa.gov/ostwater/standards/criteria/selref.html

## Acute and Chronic Toxicity Workgroup Being Formed

**	********	**EPA is currently establishing a work group that will be 	charged initially with revising the acute freshwater 		criterion and subsequently with revising the freshwater 	chronic criterion and developing site-specific criteria 	guidelines.
**	********	**As inputs to this workgroup, EPA has sponsored 		additional acute toxicity testing, has updated its 		literature review in 1998, is planning to publish new 	data on selenium effects in experimental streams, and is 	critically evaluating the tissue- residue-effects data base 	for establishing residue-based toxicological benchmarks 	for selenium.

## Additional Information?

**	********	****For more information on EPA’s revision of selenium ****	****aquatic life criteria, consult ****	****	****	****	****	****http://www.epa.gov/ost/selenium**
**	********	****contact Keith Sappington via e-mail at: ****	****	****	****sappington.keith@epa.gov**