1. 2,3,7,8-TCDD (Dioxin) Fort Detrick Dawn A. Ioven, Toxicologist U.S. EPA – Region III 2 September 2010

2. DEFINITION The term “dioxin” refers to a class of compounds with similar chemical structures, but different toxicities. The term “dioxin” refers to a class of compounds with similar chemical structures, but different toxicities. The most toxic dioxin compound is 2,3,7,8- TCDD. The most toxic dioxin compound is 2,3,7,8- TCDD. To account for toxicity differences, dioxins are measured in 2,3,7,8-TCDD equivalents (TEQ). To account for toxicity differences, dioxins are measured in 2,3,7,8-TCDD equivalents (TEQ).

3. EXAMPLE OCDD is a type of dioxin. OCDD is a type of dioxin. OCDD is 3300 times less potent than 2,3,7,8-TCDD. OCDD is 3300 times less potent than 2,3,7,8-TCDD. An OCDD concentration of 10,000 ppt is equivalent to 3 ppt of 2,3,7,8-TCDD. An OCDD concentration of 10,000 ppt is equivalent to 3 ppt of 2,3,7,8-TCDD.

4. SOURCES OF DIOXIN Incineration of waste (incomplete burning) Incineration of waste (incomplete burning) Natural processes Natural processes –Volcanic eruptions –Forest fires Industrial processes Industrial processes –Smelting –Chlorine bleaching of paper pulp –Manufacturing of some pesticides and herbicides

5. DIOXIN EXPOSURE More than 90 percent of exposure is from dietary sources: More than 90 percent of exposure is from dietary sources:

6. TOXICITY Dioxin is recognized by the World Health Organization as a Human Carcinogen Dioxin is recognized by the World Health Organization as a Human Carcinogen –Soft tissue sarcoma –Lymphoma –Multiple myeloma –Chronic lymphocytic leukemia Non-cancer health effects Non-cancer health effects –Chloracne –Liver damage –Immune system suppression –Miscarriages –Birth defects

7. U.S. EPA POSITION Current screening level for 2,3,7,8-TCDD TEQ in residential soil is 1000 ppt. Current screening level for 2,3,7,8-TCDD TEQ in residential soil is 1000 ppt. Proposed screening level for 2,3,7,8-TCDD TEQ in residential soil is 72 ppt. Proposed screening level for 2,3,7,8-TCDD TEQ in residential soil is 72 ppt.

8. DIOXIN REASSESSMENT Pending Dioxin Reassessment due for release in Spring 2011. Pending Dioxin Reassessment due for release in Spring 2011. Screening level for 2,3,7,8-TCDD may be revised when this document is released. Screening level for 2,3,7,8-TCDD may be revised when this document is released. Clean-up goals for residential soil may range from background (low ppt) to about 72 ppt. Clean-up goals for residential soil may range from background (low ppt) to about 72 ppt.

9. FORT DETRICK Recent off-site soil data provided to U.S. EPA revealed: Recent off-site soil data provided to U.S. EPA revealed: –A maximum OCDD concentration of 6060 ppt –A maximum 2,3,7,8-TCDD TEQ concentration of 7.89 ppt In rural areas of the U.S., background levels of 2,3,7,8- TCDD TEQ range up to 11 ppt. In rural areas of the U.S., background levels of 2,3,7,8- TCDD TEQ range up to 11 ppt. 2,3,7,8-TCDD (not OCDD) is associated with Agent Orange. The maximum 2,3,7,8-TCDD level in off-site soil was 0.637 ppt. 2,3,7,8-TCDD (not OCDD) is associated with Agent Orange. The maximum 2,3,7,8-TCDD level in off-site soil was 0.637 ppt. Additional on-site and off-site sampling will be Additional on-site and off-site sampling will be conducted for dioxins.