Document zoQRyV5ZZMV6BXe0yamNaLpXB

ABD00067517 November 23, 1990 DRAFT DO NOT SITE OR QUOTE A Review and Comparison of Acceptable Ambient Air Concentrations for Vinyl Chloride Based on Carcinogenicity There are two recent EPA documents in which estimates were derived for ql* values for vinyl chloride. In the first document (Health Effects Assessment for Vinyl Chloride, EPA, 1984, Office of Health and Environmental Assessment, EPA/540/1-86-036) the human ql* was determined to be 2.5xl0~a(mg/kg/day)_1. Inhalation studies in rats were used and total tumors were used as the toxicological endpoint. This ql* value can be converted to units of ppm"1 or (ug/m3)"1 as follows: 1. correction for surface area between humans and rats [(l/(70kg human/.35 kg rat))1/3] * 2.5xl0'a - 4.27 x 10'3 (mg/kg/day)"1 2. adjustment for body weight of rat 4.27xl0"3/. 35 kg rat - 1,22 x 10'2 (mg/day)"1 3. adjustment for breathing rates of rats .233 m3/d * 1.22 X 10-2 - 2.72 X 10"3 (mg/m3)"1 or 2.72 x 10'6 (ug/m3)"1 or 2.56 x 103 (ug/m3*ppm)*2.72 x 10-6 (ug/m3)"1 - 6.96 x 10"3 ppm'1 In a more recent update (Health and Environmental Effects Profile for Chloroethene, EPA, 1985, Environmental Criteria and Assessment Office ECA0Cinn-P155) the human ql* was determined to be 2.95 x 10'1 (mg/kg/day)-1. The same animal studies were used, only instead of using total tumor incidence, just angiosarcomas of the liver were used as the toxicological endpoint. Also, corrections to the dose were made since the observation period was extended after exposure stopped and an assumption was made that only 50% of the inhaled vinyl chloride was being absorbed. By using the same conversion factors above and correcting for % uptake the following inhalation ql* was determined. 1. correction for surface area between humans and rats [ (1/(70/. 35) )1/3 ] *2,95 x 10-1 (mg/kg/d)-1 - 5.05 x 10-2 (mg/kg/d)"1 ABD00067518 2. adjustment for body weight and breathing rate of rats [5.05 x 10'2 (mg/kg/d)"V.35kg]*.223 m3/ct = 3.22 x 10*2 (mg/m3)'1 or 3.22 x 10'5 (ug/m3)*1 3. In this assessment EFA assumed that only 50% of the vinyl chloride was absorbed through the lungs. To correct for this the ql* value has't to be multiplied by ,5. (.5)*3.22 x 10"5 (ug/m3)-1 - 1.61 x 10"5 (ug/m3)"1 or 4.12 x 10*2 ppm"1 -1 The state of Mississippi is recommending a ql* value of 4.2 x 10"5 (ug/m3)'1. This value is derived from the more recent EPA report just described from the ql* value of 2.95 x 10'1 (mg/kg/d)'1. As you can see this number is 2.6 fold greater than the number calculated above (1.61 x 10*5), Mississippi derived their number as follows. 1. [2.95 x 10"1 (mg/kg/d)*1]*( ,5)*(20 m3/d)*(10-3mg/ug)/70 kg - 4.21 x 10'3 (ug/m3)'1 This calculation is wrong, since they did not back calculate to the original experimental air levels of vinyl chloride. The Toxic Substances Control Program in the California Department of Health Services is currently recommending a unit risk of 7.14 x 10"2 (mg/kg/d)"1 (personal communication, Dr. John Brantner, staff toxicologist, California Department of Health Services). By using the same calculation procedure that Mississippi used and using California's assumption of 42% retention of vinyl chloride by the lungs, this converts to a ql* of 8.57 x 10'* (ug/m3)'1 (I was unable to get enough data to perform the correct calculations which would result in a lower ql*). The California Department of Health Services recommends this unit risk estimate to determine acceptable vinyl chloride levels at toxic waste sites. However, The California Air Resources Board is considering promolgating a ql* value of 20 x 10'3 ppb'1 (7.81 x 10'5 (ug/m3)'1) . I do not have the information to determine which animal studies were used In this determination. However, the use of this value would result in the lowest acceptable ambient air concentration. The following table provides the ql* values currently used by various states in setting ambient air concentrations considered to provide an acceptable cancer risk of 10"6. State unit risk (ql*) (ug/mm3)'1 acceptable exposure (cancer risk of 10'*) ABD00067519 A KS .26 x 10'6 3.85 KS-KC MA MI NC NY PA-Phil TX VT EPA (old) EPA (new) CA (toxic Substances Control Program) CA (proposed by Air Resources Board) MS 4.1 2.6 2.5 2.6 2.5 0.16 0.10 5.00 2.72 16,1 8.57 78.1 42 .24 ,38 .40 .38 .40 6.25 10. .20 .37 .06 .11 .01 .02 As you can see from this cable many of the states are using EPA's old ql* value for determining levels not to exceed a cancer risk of 10"6. If one uses the new EFA ql* the acceptable levels would have to be reduced by a factor of 6 over the old estimates. In setting the new ql*, however, the data used looks very supiclous. For example, ql* was calculated using these data points from the rat inhalation studies; transformed dose corrected for average dose amount absorbed incidence (liver angiosarcoma) No. respondlng/No. tested or examined 0.344 mg/kg/day 1/119 0.860 5/120 1.719 1/60 3.438 1/120 ABD00067520 4 As you can see their is no dose response relationship and by substituting these points into the statistical GLOBAL program to calculate a unit risk doesn't make sense. Toxicologists have raised several questions about the animal inhalation studies by Maltoni used in the EPA calculations and they may not be the appropriate studies to use. The EPA ql* values have not undergone any credible scientific peer review. The most recent document (EFA/600/x85/374 September 1985) in which the most conserative ql* value of 16,1 x 10"6 (ug/m3)_1 was obtained and used by the State of Mississippi is an external draft and the disclaimer states it does not constitute Agency Policy. However, the earlier EPA document (EPA/540/1-86-036, September 1984) which has the ql* value of 2.5 x 10~2 (mg/kg/d)"1 does not have this disclaimer, and therefore on policy grounds, should be the one that the Agency recommends using. However, even this number [2.5 x 10"2 (mg/kg/d)"1] can be challenged because it has not undergone any public comment period or any official regulatory sign-off authority within the Agency. The following arguments can be made to discard Mississippi's ql* value of 42 x 10"6 (ug/m3)*1. 1. The calculation performed was on a ql* value that EPA has not officially endorsed. There is no ql* value given in the IRIS data base for vinyl chloride. 2. The conversion mg/kg/d to ug/m3 that the Mississippi Department of Environmental Quality used was incorrect. The right conversion would decrease the ql* value by 2.6. 3. The data used in calculating the higher EPA ql* value is not of sufficient quality to determine a ql* value. 4. The Maltoni inhalation data used by EPA in both reports may not be of sufficient quality to perform a quantitative risk assessment for vinyl chloride. 5. YOU HAVE GOOD GROUNDS TO ARGUE FOR THE LOWER Ql*! The bigger problem may lie in California and .could effect other states if they adopt the Air Resources Board proposed ql* of 20 x 10-5 ppV1. This could be addressed through public comments, and meetings, possibly through your company and/or the Vinyl Institute.