Consumer product safety: Risk assessment of exposure to asbestos emissions from hand-held hair dryers

The United States Consumer Product Safety Commission (CPSC) is concerned that consumer exposure to asbestos from consumer products may present an unreasonable risk of injury. Recently, CPSC has obtained agreement by industry to cease production and distribution of hair dryers containing asbestos heat insulation. CPSC intends to broaden its investigation by selecting consumer products containing asbestos for priority attention. The Commission does not intend to make quantitative estimates of cancer risks posed by exposure to asbestos fibers in making regulatory decisions. This position may lead to a serious waste of resources for the Commission, industry, and society. The Commission should focus its initial attention on those products for which the release of asbestos is significant enough to cause an unreasonable health risk. To make a risk assessment for a particular use of asbestos, CPSC must acquire or request data on asbestos emissions and define unreasonable risk to health.In an attempt to give some meaning to the phrase risk assessment, the primary goal of this paper is to present a detailed risk assessment of exposure to asbestos from hand-held hair dryers. Several scenarios of use are presented using various assumptions regarding time of operation, mixing of fibers in a small room, rate of fiber emission, and time of exposure. The worst case analysis of the health risk of exposure to hair dryer emissions is based on several conservative assumptions and shows that the increased number of deaths per year due to respiratory cancer is 4 for the entire United States population. A more representative case analysis shows the increased number of deaths to be on the order of 0.15 per year.     

CRITIQUE—Consumer product safety: Risk assessment of exposure to asbestos emissions from hand-held hair dryers

The paper by Dr. William Hallenbeck of the University of Illinois on pp. 23–32 of this issue ofEnvironmental Management contains an estimate of the risk of respiratory cancer resulting from exposure to asbestos fibers emitted from asbestos-containing hairdryers. The study, which is described as a worst case analysis, concludes that the use of these hairdryers would result in a maximum of 0.15 deaths from respiratory cancer per year in the United States, based on a median case estimate of asbestos fiber emission from hair-dryers. This estimate of risk was developed using data from one epidemiologic study.In this critique, we suggest that the use of other epidemiologic studies and the inclusion of other minor, reasonable changes to the basic assumptions made by Hallenbeck could significantly change the estimate in the direction of greater risk. Indeed, the use of other epidemiologic studies in the risk estimate results in an increase in the predicted risk of up to 3 orders of magnitude. Inclusion of changes both in the epidemiologic study used and in certain model assumptions results in an increased risk prediction of over 4 orders of magnitude in the extreme.Since there is no definitive basis on which to include or exclude certain assumptions or relevant studies, the risk estimate at best must be represented as a range of values. Such a range demonstrates the inherent uncertainties associated with estimating the risk to humans from known carcinogens. The size of the range developed in this analysis may actually be underestimated since no attempt has been made to evaluate the uncertainty associated with the choice of the dose-response model.The material found within this paper contains the views of the authors who are employees of the Consumer Product Safety Commission and does not necessarily reflect official opinions or policies of the U.S. Consumer Product Safety Commission.This paper was prepared in the course of the official duties of the authors as employees of the U.S. Consumer Product Safety Commission. It is in the public domain and may be freely copied and reproduced.     

Contrasting pathways of assimilation: stable isotope assessment of fish exposure to pulp mill effluents

Fish are commonly used for monitoring the quality of waters receiving pulp mill effluents (PMEs). Isotopic assays of fish tissues have the potential to provide empirical evidence to link an effluent source to exposure. We show in a 45-d factorial laboratory experiment that different exposure pathways lead to isotopic signatures in fish tissue. Rainbow trout (Oncorhynchus mykiss) were exposed to 10% PME in three ways; direct exposure through addition of PME to aquaria, indirect exposure through invertebrate food consumption (Chironomus tentans cultured in 10% PME), and a combination of both exposure pathways. Of the four stable isotopes measured (delta13C, delta15N, delta34S, delta37Cl), delta13C, delta34S, and delta37Cl showed significant differences in exposed animal tissues. Delta37Cl of fish muscle tissue showed consistent differences across trophic levels and revealed contrasting pathways of PME exposure. Contrasting delta 37Cl values in C. tentans due to the presence or absence of 10% PME did not translate into delta37Cl differences in fish. Rather, delta37Cl ratios of fish muscle tissue were specifically related to 10% PME exposure in the aquaria (waterborne exposure pathway). Feasible distributions of 37Cl source contributions for observed mixture ratios confirmed that PME accounted for observed differences in delta37Cl among treatments. Direct uptake of chloride ions across gill surfaces is the most likely pathway for assimilation of PME into fish tissues. Considering the variability of PMEs and receiving environments, use of a multi-isotope approach is recommended for tracing exposure of fish. Use of 37Cl should also be considered in light of its alternative assimilation pathway.     

Estimation of annual CH4 and N2O emissions from fluidised bed combustion: An advanced measurement-based method and its application to Finland

The aim of this study was to develop and apply an advanced, measurement based method for the estimation of annual CH₄ and N₂O emissions and thus gain improved understanding on the actual greenhouse gas (GHG) balances of combustion of fossil fuels, peat, biofuels and REF. CH₄ and N₂O emissions depend strongly on combustion conditions, and therefore the emission factors used in the calculation of annual emissions contain significant uncertainties. Fluidised bed combustion (FBC) has many good properties for combustion of different types of fuels and fuels of varying quality, e.g., biofuels and wastes. Therefore, it is currently increasing its market share. In this study, long term measurements (up to 50 days) were carried out at seven FBC boilers representing different size classes, loadings and fuel mixes. Both decreasing load and increasing share of coal in fuel mix increased N₂O emissions. Measurement results from different loading levels were combined with the common loading curves of similar plants in Finland to estimate annual emissions. Based on the results, recommendations for emission factors for the Finnish GHG emission inventory are given. The role of FBC as a potential technology for the utilisation of biofuels and wastes with future GHG reduction requirements is discussed.