The Department of Environmental Protection has revised the toxicity equivalence factors (TEFs) used with the dioxin air quality guideline as originally established in 1985 (1)(2) and updated in 1989 (3). The recommended changes in the TEFs shown in Attachment 1 are intended to incorporate current information on the toxicities of the chemicals comprising the polychlorinated dibenzodioxins (PCDDs) and dibenzofurans (PCDFs). The revisions do not change the level of public heath protection. The Department will continue to review resource recovery facilities and municipal incinerators against the guideline. The revisions are viewed as conservative and protective of public health with an adequate margin of safety.

Summary of the Air Quality Guideline

The Massachusetts dioxin air guideline is expressed, on a toxic equivalence basis, as "total polychlorinated dibenzodioxins and polychlorinated dibenzofurans" and shall not exceed a toxic equivalent concentration of 0.045 picograms per cubic meter (pg/m3). The guideline is an annual average and remains the same with the new revisions to the TEFs.

Toxic equivalency factors are used to evaluate the toxicity of complex environmental mixtures containing PCDDs and PCDFs. TEFs are used to mathematically convert the concentration of PCDDs and PCDFs to an equivalent concentration of 2,3,7,8-tetrachlorodibenzo- p-dioxin (2,3,7,8-TCDD).

The TEFs used in establishing the 1989 dioxin air guideline were selected from a study conducted by the Swiss Government in 1982. The changes represented by the revised TEFs are based on the large body of toxicity data which has become available since 1982. The Attachment 2 prepared by the Office of Research and Standards summarizes this information.

The dioxin air guideline is set at a level at which no non- cancer health effects would be expected as a result of lifetime exposure. The guideline concentration is associated with an individuals excess lifetime cancer risk as low as zero and possibly as high as 5.9 in one million.

The revised TEFs were reviewed at the June meeting of the DEP/DPH Advisory Committee on Heath Effects. The comments of committee members were incorporated into the recommended TEFs.

(Signed by the Commissioner October 31, 1991)
__________________________ Daniel S. Greenbaum
Commissioner
Department of Environmental Protection, 1991

References

Assessment and Control of Dioxin Emissions in Massachusetts, S. Russell Sylva, Commissioner DEQE, October 23, 1985.

Derivation of Ambient Air Quality Guidelines for Dioxins, Carol Rowan West and Michael J. Murphy, DEQE Office of Research and Standards, August 4, 1986.

Revision of the September 20, 1985 Dioxin Air Guideline, Michael J. Murphy, Office of Research and Standards, February 7, 1989.

Attachments

Attachment 1. Summary - Toxicity Equivalency Factors

CompoundEPA/89Old DEPNew DEP
Mono-, Di- and TriCDDs00.01(Tri only)0.001
2,3,7,8-TCDD
Other TCDDs
1
0
1
0.01
1
0.01
2,3,7,8-PeCDD
Other PeCDDs
0.5
0
0.1
0.1
0.5
0.05
2,3,7,8-HxCDD
Other HxCDDs
0.1
0
0.1
0.1
0.1
0.01
2,3,7,8-HpCDD
Other HpCDDs
0.01
0
0.01
0.01
0.1
0.01
OCDD0.001None Assigned0.001
Mono-, Di- and TriCDFs00.01(Tri only)0.001
2,3,7,8-TCDF
Other TCDFs
0.1
0
0.1
0.1
0.1
0.01
1,2,3,7,8-PeCDF
2,3,4,7,8-PeCDF
2,3,7,8-PeCDFs
Other PeCDFs
0.05
0.5
0
0


0.1
0.1


0.5 *
0.05
2,3,7,8-HxCDFs
Other HxCDFs
0.1
0
0.1
0.1
0.1
0.01
2,3,7,8-HpCDFs
Other HpCDFs
0.01
0
0.01
0.01
0.1
0.01
OCDF0.001None Assigned0.001
 
* includes 1,2,3,7,8-PeCDF and 2,3,4,7,8-PeCDF

Attachment 2: