Assessing potential health risks
of dioxin in paper products
By Russell E. KeeMn and Michael J. Sullivan The presence of trace quantities of dioxin in bleached paper and pulp based products has raised concern over whether exposure to these sources can significantly affect people's health. To address this question, a formal risk assessment was performed to evaluate potential dioxin exposure through derRussell Keenan mal contact with bleached pulpbased communication paper and personal care products. Trace concentrations of 2,3,7,8tetrachlorodibenzo-p-dioxin (TCDD) and 2,3,7,8-tetrachlorodibenzofuran (TCDF) have been measured in some samples of bleached pulp and in some products manufactured from bleached pulp. In one study (I), seven of nine bleached pulp samples were found to contain TCDD at levels ranging up to 51 parts per trillion (ppt) (median of 4.9 ppt, mean of 13 ppt). Eight of nine bleached pulp samples had TCDF levels ranging up to 330 ppt (median of 50 ppt, mean of 93 ppt). In subsequent analyses (2). trace levels of TCDD and Mickael Sullivan TCDF were found in some composites of several bleached pulpbased products. For example, a bond paper com- verse health effects from human posite had mean levels of 13 ppt TCDD exposures to environmental hazards. and 265 ppt TCDF, and a paper towel The formal risk assessment process has composite had mean levels of 3.8 ppt four components: hazard identification, TCDD and 33 ppt TCDE A composite dose-response assessment, exposure of diaper pulp showed no detectable assessment, and risk characterization. TCDD, but did contain TCDF at a This paper summarizes the results of mean concentration of 8.0ppt. our risk assessment. This risk assessment followed the procedures outlined by EPA (3) and the Hazard identification Hazard identification is a qualitative National Academy of Sciences (NAS) analysis of the animal toxicity and hu(4). Chemical risk assessment, as defined by NAS (4, is the characteriza- man health effects literature. For car. tion of the probability of potentially ad- cinogen risk assessments, hazard iden W13936W89/09Z30643501.50/0 @ 1989 American Chemical Sociehl
tification is the process of determining whether exposure to a chemical could cause an increase in the incidence of cancer. The potential health effect of primary concern in the case of exposure to dioxin is carcinogenicity. Exhaustive reviews of the dioxin health effects literature exist (5-7). Readers should consult those reviews for detailed information on dioxin health effects. Dose~esponseassessment
The dose-response assessment is the quantitativecharacterizationof the relationship between the dose of an agent and the incidence of an adverse health effect in the exposed population (4). The result of the dose-response assessment is a probability estimate of the incidence of the effect associated with a given dose and route of exposure. EPA and the Food and DNg Administration (FDA) have used the upper 95% confidence interval of a linear dose-response model to estimate dioxin cancer potency. EPA used the linearized multistage model (7)and FDA (8) used the Gaylor-Kodell (9) linear interpolation model. These models assume that there is some risk, however small, associated with any dose of a chemical or agent. Therefore, both models are considered to be nonthreshold models of carcinogenic dose response. The FDA cancer potency of 1.75 x I@ (mg/kg/day)-' was selected for use in this analysis for several reasons. It is the potency used by a federal agency with regulatory authority. It is based on laboratory animal data on the most sensitive sex, strain, and "Or (IO).FDA adjusted for dose between rats and humans using body weight, not surface area. FDA conservatively used the u p Envimn. Sci. Technol.. Vol. 23, No. 6, 1989 643
per 95 % confidence interval of a linear slope to model the dose-response relationship. We agree with FDA that their cancer potency estimate is fully protective of public health.
Exposure assessment The exposure assessment consists of defining the exposed population and measuring or estimating the frequency, duration, and intensity of exposure. Several components of the exposure assessment warrant discussion. Detailed product-use patterns including contact duration and frequency of use were analyzed to derive the product-use estimates for the assessment. Models of potential dioxin uptake for both dry and wet contact with these products were developed. For the wet contact model, actual partition coefficients between pulp and model fluids (water, physiclogical saline, and synthetic urine) were determined in laboratory studies. These partition coefficients were used to estimate the potential migration of dioxin in these products into the fluid contacting the pulp. Ultimately, only the dioxin that partitions into the fluid and subsequently comes into direct contact with the skin is available for uptake. Also, the bioavailability of dioxin through dermal exposure was estimated. The risk assessment evaluated potential dioxin exposure through dermal contact associated with the normal use of communication papers, including writing paper, copy paper, newspapers, and magazines; and personal care products, including disposable diapers, facial tissues, toilet tissue, paper towels, and sanitary pads (2). €"duct-use estimates for a representative female are presented in Table 1. Risk eharacterizatinn Risk characterization is the process of estimating the incidence of a health 644 Environ. Sci. Technol., Vol. 23,NO. 6, 1989
effect under the various conditions of exposure described in the exposure assessment. It is performed by combining the dose-response and exposure assessments. In this risk assessment, the upper bound incremental risk level of 1 in 1,ooO,ooO (1 x 1W)has been used. This level clearly represents the de minimis or insignificant risk level for exposure to environmental agents. Using this risk level, the FDA cancer p tency, and the results of the exposure assessment, we calculated the themetical allowable concentration of TCDD and its toxic equivalents (11) in each product. Because this allowable concentration is specific to the selection of a level of incremental risk, it is referred to as the risk-specific concentration (RSC). Table 1 lists the calculated RSCs associated with an upper bound incremental risk level of 1 x 10" for a representative female. The productspecific RSCs range from 4200 to 66,ooO,ooOppt TCDD equivalents.
Conelusions The results of the risk assessment performed on bleached pulp-based communication papers and personal care products show that the productspecific RSCs are orders of magnitude greater than concentrations of dioxin that actually have been measured in these products. That is, concentrations of dioxin in these products could be orders of magnitude larger than measured, and the upper bound risk would still remain insignificant at less than 1 x IW".This means there is a large margin of safety for the continued use of the bleached pulpbased products addressed in this assessment. References (1) Amendola, 0. et al. Presented at the 7th International Symposium on Chlorinated Dioxins and Related Compounds, Las Vegas, NV, 1987.
(2) "Assessment of Potential Health Risks from Dermal Exposure to Dioxin in Paper Products"; Technical Bulletin No, 534, 1987; Prepared by Envirologic Data for the National Council of the Paper Industry for Air and Stream Improvement, New York. (3) Fed. Regist. 1986, 15(185), 3399234003. (4) Risk Assessment in the Fedeml Government: Managing the Proccss; Committee on the Institutional Means for Assessment of Risks to Public Health, National Research Council. National Academy Press: Washington, DC, 1983. ( 5 ) "Dioxin: A Critical Review of its Distribution, Mechanism of Action Impacts on Human Health, and the Setting of Acceptable Exposure Limits"; Technical Bulletin No. 524, 1987; Prepared by ENVIRON for National Council of the Paper Industry for Air and Stream Improvement, New York. (6) Fisbein, L. "Health-Risk Estimates for 2,3,7,8-Tetrachloro-Dibe~odioxin: An Overview.*' Tozicol. Ind. Health 1987.3, 91-134. (7) Health Assessment Document for Polychlorinated Dibenro-p-dimins; Office of Health and Environment. U S . Environmental Protection Agency: US. Government Printing Office: Washington, DC, 1985, EPA/MX)/8-84/014F, (8) Scheuplein, R. I n Public Health Risks of the Dioxins; Lowrance, W., Ed.; Proceedings of Symposium at Rockefeller University, New York; William Kaufman: L w Altos, CA, 1984; pp. 367-72. (9) Gaylor, D. W.; Kodell, R. L. 3. Environ. Pnthol. Toxcol. 1980,4, 305-12. (IO) Kwiba, R. 1. et al. Toxicol. Appl. Phnrmacol. 1578.46, 279-303. (11) Interim Procedures for Estimating Risks Associated with Exposures to Mixtures of Chlorinated Dibenro-p-Dioxins and -Dibeneofurons (CDD8 ond CDFs); Risk Assessment Forum. U.S. Environmental Protection Agency; U.S. Government Printing Office: Washington, DC, 1987; EPA/625/3-87/012.
Russell E. Keenan is principal roxicologist and regional manager of the easrem division of McLaren ChemRisk" in Portland, ME. He has assessed potential health risksfrom exposure to dioxin in wastewater sludge and efluent, paperproducts, and resource recovery incinerators. He obtained his Ph.D. from Duke University and has over 13 years of experience as a biologist and toxicologist. In his previous position he was corporate director of the risk assessmen?divisionfor Envirologic Data. Michael J. Sullivan is regional director of the risk assessment division, West Region, of Envirologic Data in Vmrura, CA. His areas of expertise include environmental and industrial toxicological issues. He obtained his Ph.D. from the University of Michigan and has over 10 years of experience in toxicology, including two years as toxicology program manager for the National Council of the Paper Industry for Air and Stream Improvement.
