Connecticut's Dioxin Ambient Air Quality Standard

Connecticut is the first state in the country to have adopted an ambient air quality standard for dioxins at 1 pg/m³, 2,3,7,8-TCDD equivalents, as annual average. This paper describes the scientific basis and the methodology used by the State Department of Health Services (the risk assessment agency) in assisting the Department of Enviromental Protection (the risk management agency) to establish a health-based dioxin standard. This standard protects the public health from the aggregate effect of all sources of dioxin emissions in the vapor and particulate phases. The risk assessment methodology included: a limit on total daily dioxin exposure from all media and sources based on reproductive effects; a multimedia nonsource-specific exposure assessment; an apportionment by media of the health-based limit (including background dosing rate); an evaluation of inhalation bioavailability and cancer risk based on a calculation of a range of upperbound cancer risk estimates using different potency, bioavailability, and particle phase assumptions.     

Exposure to Persistent Organochlorines in Canadian Breast Milk: A Probabilistic Assessment

Exposure to persistent organochlorines in breast milk was estimated probabilistically for Canadian infants. Noncancer health effects were evaluated by comparing the predicted exposure distributions to published guidance values. For chemicals identified as potential human carcinogens, cancer risks were evaluated using standard methodology typically applied in Canada, as well as an alternative method developed under the Canadian Environmental Protection Act. Potential health risks associated with exposure to persistent organochlorines were quantitatively and qualitatively weighed against the benefits of breast-feeding. Current levels of the majority of contaminants identified in Canadian breast milk do not pose unacceptable risks to infants. Benefits of breast-feeding are well documented and qualitatively appear to outweigh potential health concerns associated with organochlorine exposure. Furthermore, the risks of mortality from not breast-feeding estimated by Rogan and colleagues exceed the theoretical cancer risks estimated for infant exposure to potential carcinogens in Canadian breast milk. Although levels of persistent compounds have been declining in Canadian breast milk, potentially significant risks were estimated for exposure to polychlorinated biphenyls, dibenzo-p-dioxins, and dibenzofurans. Follow-up work is suggested that would involve the use of a physiologically based toxicokinetic model with probabilistic inputs to predict dioxin exposure to the infant. A more detailed risk analysis could be carried out by coupling the exposure estimates with a dose–response analysis that accounts for uncertainty.     

Estimation of Human Exposure from Fish Contaminated with Dioxins and Furans Emitted by a Resource-Recovery Facility

Ingestion of contaminated fish can be an important human exposure pathway for dioxins and furans emitted from waste incineration plants. A new method for calculating fish contamination resulting from dioxin and furan emissions has been developed to overcome some of the problems of those currently used. The method is based on evidence that the major determinant of fish dioxin and furan uptake is sediment concentrations. Only two steps are necessary to calculate fish tissue levels. Step 1: Calculation of the concentration of dioxins and furans in particulate matter entering the lake or pond, and hence, the resulting sediment concentration. Step 2: Calculation of fish concentrations utilizing fish-to-sediment ratios for the various dioxin and furan isomers.     

Risks of Municipal Solid Waste Incineration: An Environmental Perspective

The central focus of the debate over incineration of municipal solid waste (MSW) has shifted from its apparent management advantages to unresolved risk issues. This shift is a result of the lack of comprehensive consideration of risks associated with incineration. We discuss the need to expand incinerator risk assessment beyond the limited view of incinerators as stationary air pollution sources to encompass the following: other products of incineration, ash in particular, and pollutants other than dioxins, metals in particular; routes of exposure in addition to direct inhalation; health effects in addition to cancer; and the cumulative nature of exposure and health effects induced by many incinerator-associated pollutants. Rational MSW management planning requires that the limitations as well as advantages of incineration be recognized. Incineration is a waste-processing--not a waste disposal--technology, and its products pose substantial management and disposal problems of their own. Consideration of the nature of these products suggests that incineration is ill-suited to manage the municipal wastestream in its entirety. In particular, incineration greatly enhances the mobility and bioavailability of toxic metals present in MSW. These factors suggest that incineration must be viewed as only one component in an integrated MSW management system. The potential for source reduction, separation, and recycling to increase the safety and efficiency of incineration should be counted among their many benefits. Risk considerations dictate that alternatives to the use of toxic metals at the production stage also be examined in designing an effective, long-term MSW management strategy.     

Dioxin in the Agricultural Food Chain

Polychlorinated dibenzo-p-dioxin's (PCDD) behavior in the agricultural food chain was modeled in this study. The source of PCDD was a municipal solid waste (MSW) incinerator. Of the farm livestock investigated only the beef cow and the milk cow were shown to contribute significant amounts of PCDD to humans. Milk was the single highest dietary source of PCDD. Comparison of the calculated human dose of PCDD from the agricultural food chain with an estimate human PCDD dose from inhalation of contaminated air revealed that the agricultural food chain could be responsible for a vast majority of the dose to an individual impacted by these facilities. Thus, these data suggest that operating MSW facilities in agricultural areas may result in enhanced PCDD exposure to individuals via the agricultural food chain. The data also suggest that milk and beef may be good sentinels to evaluate environmental impacts of these facilities.     

Costs of Health Damage from Atmospheric Emissions of Toxic Metals: Part 1—Methods and Results

Significant quantities of toxic metals are emitted to the air by the incineration of waste, as well as by the combustion of coal and oil. To optimize the regulations for their emissions one needs to know the cost of their damage. That requires an impact pathway analysis, with realistic dispersion models, exposure‐response functions, and monetary values. In this article we explain the method and assumptions and present results for arsenic, cadmium, mercury, and lead, the most important toxic metals in terms of damage cost. We also estimate their contribution to the damage cost of waste incineration and electric power from coal for typical situations in Europe. The damage costs of As, Cd, and Pb are much higher than previous estimates because of a large number of new epidemiological studies, implying more and more serious health effects than what had been known before. New cost‐benefit studies for the abatement of toxic metal emissions are advisable. The discussion of the epidemiological studies and the derivation of exposure‐response functions are presented in two companion articles, one for As and Cd, the other for Hg and Pb.     

Development and Application of a Probabilistic Risk–Benefit Assessment Model for Infant Feeding Integrating Microbiological,Nutritional, and Chemical Components

A probabilistic and interdisciplinary risk–benefit assessment (RBA) model integrating microbiological, nutritional, and chemical components was developed for infant milk, with the objective of predicting the health impact of different scenarios of consumption. Infant feeding is a particular concern of interest in RBA as breast milk and powder infant formula have both been associated with risks and benefits related to chemicals, bacteria, and nutrients, hence the model considers these three facets. Cronobacter sakazakii, dioxin‐like polychlorinated biphenyls (dl‐PCB), and docosahexaenoic acid (DHA) were three risk/benefit factors selected as key issues in microbiology, chemistry, and nutrition, respectively. The present model was probabilistic with variability and uncertainty separated using a second‐order Monte Carlo simulation process. In this study, advantages and limitations of undertaking probabilistic and interdisciplinary RBA are discussed. In particular, the probabilistic technique was found to be powerful in dealing with missing data and to translate assumptions into quantitative inputs while taking uncertainty into account. In addition, separation of variability and uncertainty strengthened the interpretation of the model outputs by enabling better consideration and distinction of natural heterogeneity from lack of knowledge. Interdisciplinary RBA is necessary to give more structured conclusions and avoid contradictory messages to policymakers and also to consumers, leading to more decisive food recommendations. This assessment provides a conceptual development of the RBA methodology and is a robust basis on which to build upon.     

Lactational Transfer of Tetrachloroethylene in Rats

Tetrachloroethylene (PCE) is a commonly used organic solvent and a suspected human carcinogen, reportedly transferred to human breast milk following inhalation exposure. Transfer of PCE to milk may represent a threat to the nursing infant. A physiologically based pharmacokinetic (PBPK) model was developed to quantitatively assess the transfer of inhaled PCE into breast milk and the consequent exposure of the nursing infant. The model was validated in lactating rats. Lactating Sprague-Dawley female rats were exposed via inhalation to PCE at concentrations ranging from 20-1000 ppm, and then returned to their nursing, 10- to 11-day-old pups. Tetrachloroethylene concentrations in the air, blood, milk, and tissue were determined by gas chromatography and compared to model predictions. The model described the distribution of inhaled PCE in maternal blood and milk, as well as the nursed pup's gastrointestinal tract, blood, and tissue. Several computer simulations of PCE distribution kinetics in exhaled air, blood, and milk of exposed human subjects were run and compared with limited human data available from the literature. It is concluded that the PBPK model successfully described the concentration of PCE in both lactating rats and humans. Although predictions vs. observations were good, the model slightly underpredicted the peak whole pup PCE concentration and underpredicted systemic clearance of PCE from the pup.     

Uncertainty and Variation in Indirect Exposure Assessments: An Analysis of Exposure to Tetrachlorodibenzo-p-Dioxin from a Beef Consumption Pathway

Indirect exposures to 2,3,7,8-tetrachlorodibenzo- p -dioxin (TCDD) and other toxic materials released in incinerator emissions have been identified as a significant concern for human health. As a result, regulatory agencies and researchers have developed specific approaches for evaluating exposures from indirect pathways. This paper presents a quantitative assessment of the effect of uncertainty and variation in exposure parameters on the resulting estimates of TCDD dose rates received by individuals indirectly exposed to incinerator emissions through the consumption of home-grown beef. The assessment uses a nested Monte Carlo model that separately characterizes uncertainty and variation in dose rate estimates. Uncertainty resulting from limited data on the fate and transport of TCDD are evaluated, and variations in estimated dose rates in the exposed population that result from location-specific parameters and individuals'behaviors are characterized. The analysis indicates that lifetime average daily dose rates for individuals living within 10 km of a hypothetical incinerator range over three orders of magnitude. In contrast, the uncertainty in the dose rate distribution appears to vary by less than one order of magnitude, based on the sources of uncertainty included in this analysis. Current guidance for predicting exposures from indirect exposure pathways was found to overestimate the intakes for typical and high-end individuals.     

Physiologically Based Pharmacokinetic Modeling of the Lactational Transfer of Methylmercury

The developmental neurotoxicity of methylmercury (MeHg) in humans has been described following catastrophic events in Minamata Bay, Japan and in Iraq, and following the exposure to lower doses elsewhere in the world. The most common route of MeHg exposure in humans is through the intake of contaminated food, especially fish. Although the precautions against the ingestion of potentially contaminated food during pregnancy are well recognized, precautions against the ingestion of MeHg during lactation are not so uniformly recognized. However, the continued development of the central nervous system during the early postnatal period serves to prolong the period during which this critical system is susceptible to the toxic insult of MeHg. Because no direct method is available to quantitatively assess the lactational transfer of MeHg to humans, a computer-aided simulation method was developed. An available gestational physiologically based pharmacokinetic model was refined and expanded to include parameters and algorithms specific for the elimination of MeHg in breast milk. The predictions of the completed model were compared with experimental data obtained from rodents, and the model parameters were allometrically scaled to humans. Finally, the model was validated by comparing its predictions against the available clinical data for MeHg distribution and elimination in mothers and their nursing infants. This model incorporated current and previous maternal exposures to MeHg to accurately predict the kinetics of MeHg excretion in breast milk and the daily intake by the nursing infant. This model may be used to quantify MeHg intake by the nursing infant, under different rates of maternal MeHg ingestion.     

Hazardous Waste Incineration at Sea: EPA Decision Making on Risk

This paper critiques the Environmental Protection Agency's assessment of risk for hazardous waste incineration at sea. It reviews operational and transportation risks and considers alternative approaches for managing chlorinated organic hazardous wastes. It concludes that depending on the scale of the program, ocean incineration will either contribute little to the overall management of this waste stream or else it will engender significant risks, especially in the coastal environment. Furthermore, past assessments on the part of EPA have tended to understate the risks of incineration at sea while simultaneously holding out the promise of the technology as a commercial-scale management option. Finally, this paper observes that the Western European countries that pioneered incineration in the North Sea are now finding practical alternatives. It is recommended that waste reuse, on-site treatment, and techniques of waste reduction provide viable alternatives and obviate the need for incineration at sea.     

Intake fraction for multimedia pollutants: a tool for life cycle analysis and comparative risk assessment.

We employ the intake fraction (iF) as an effective tool for expressing the source-to-intake relationship for pollutant emissions in life cycle analysis (LCA) or comparative risk assessment. Intake fraction is the fraction of chemical mass emitted into the environment that eventually passes into a member of the population through inhalation, ingestion, or dermal exposure. To date, this concept has been primarily applied to pollutants whose primary route of exposure is inhalation. Here we extend the use of iF to multimedia pollutants with multiple exposure pathways. We use a level III multimedia model to calculate iF for TCDD and compare the result to one calculated from measured levels of dioxin toxic equivalents in the environment. We calculate iF for emissions to air and surface water for 308 chemicals. We correlate the primary exposure route with the magnitudes of the octanol-water partition coefficient, Kow, and of the air-water partitioning coefficient (dimensionless Henry constant), Kaw. This results in value ranges of Kow and Kaw where the chemical exposure route can be classified with limited input data requirements as primarily inhalation, primarily ingestion, or multipathway. For the inhalation and ingestion dominant pollutants, we also define empirical relationships based on chemical properties for quantifying the intake fraction. The empirical relationships facilitate rapid evaluation of many chemicals in terms of the intake. By defining a theoretical upper limit for iF in a multimedia environment we find that iF calculations provide insight into the multimedia model algorithms and help identify unusual patterns of exposure and questionable exposure model results.     

What Are the Sources of Exposure to Eight Frequently Used Phthalic Acid Esters in Europeans?

Phthalic acid esters (phthalates) are used as plasticizers in numerous consumer products, commodities, and building materials. Consequently, phthalates are found in human residential and occupational environments in high concentrations, both in air and in dust. Phthalates are also ubiquitous food and environmental contaminants. An increasing number of studies sampling human urine reveal the ubiquitous phthalate exposure of consumers in industrialized countries. At the same time, recent toxicological studies have demonstrated the potential of the most important phthalates to disturb the human hormonal system and human sexual development and reproduction. Additionally, phthalates are suspected to trigger asthma and dermal diseases in children. To find the important sources of phthalates in Europeans, a scenario-based approach is applied here. Scenarios representing realistic exposure situations are generated to calculate the age-specific range in daily consumer exposure to eight phthalates. The scenarios demonstrate that exposure of infant and adult consumers is caused by different sources in many cases. Infant consumers experience significantly higher daily exposure to phthalates in relation to their body weight than older consumers. The use of consumer products and different indoor sources dominate the exposure to dimethyl, diethyl, benzylbutyl, diisononyl, and diisodecyl phthalates, whereas food has a major influence on the exposure to diisobutyl, dibutyl, and di-2-ethylhexyl phthalates. The scenario-based approach chosen in the present study provides a link between the knowledge on emission sources of phthalates and the concentrations of phthalate metabolites found in human urine.     

Major Sources of Exposure to Benzene and Other Volatile Organic Chemicals1,2

The major sources of human exposure to about a dozen volatile organic chemicals (VOCs) have recently been identified.¹ For nearly every chemical, the major sources of exposure are completely different from the major sources of emissions. This finding implies that current environmental regulations and control strategies are misdirected. Important sources of exposure are typically not regulated in any way, whereas unimportant sources are heavily regulated. Vast sums of money are spent on problems involving little risk (e.g., hazardous waste sites), whereas few resources are expended on problems involving higher risk (e.g., indoor air pollution). The following paper summarizes recent findings regarding major sources of exposure to several VOCs. Benzene is selected as a case study. Brief discussions of tetrachloroethylene and paradichlorobenzene are also included.     

A Comparative Pharmacokinetic Estimate of Mercury in U.S. Infants Following Yearly Exposures to Inactivated Influenza Vaccines Containing Thimerosal

The use of thimerosal preservative in childhood vaccines has been largely eliminated over the past decade in the United States because vaccines have been reformulated in single‐dose vials that do not require preservative. An exception is the inactivated influenza vaccines, which are formulated in both multidose vials requiring preservative and preservative‐free single‐dose vials. As part of an ongoing evaluation by USFDA of the safety of biologics throughout their lifecycle, the infant body burden of mercury following scheduled exposures to thimerosal preservative in inactivated influenza vaccines in the United States was estimated and compared to the infant body burden of mercury following daily exposures to dietary methylmercury at the reference dose established by the USEPA. Body burdens were estimated using kinetic parameters derived from experiments conducted in infant monkeys that were exposed episodically to thimerosal or MeHg at identical doses. We found that the body burden of mercury (AUC) in infants (including low birth weight) over the first 4.5 years of life following yearly exposures to thimerosal was two orders of magnitude lower than that estimated for exposures to the lowest regulatory threshold for MeHg over the same time period. In addition, peak body burdens of mercury following episodic exposures to thimerosal in this worst‐case analysis did not exceed the corresponding safe body burden of mercury from methylmercury at any time, even for low‐birth‐weight infants. Our pharmacokinetic analysis supports the acknowledged safety of thimerosal when used as a preservative at current levels in certain multidose infant vaccines in the United States.     

Chloroform Exposure and the Health Risk Associated with Multiple Uses of Chlorinated Tap Water

Recently, showers have been suspected to be an important source of indoor exposure to volatile organic compounds (VOC). The chloroform dose to an individual from showering was determined based on exhaled breath analysis. The postexposure chloroform breath concentration ranged from 6.0-21 micrograms/m3, while all corresponding background breath concentrations were less than 0.86 micrograms/m3. The internal dose from showering (inhalation plus dermal) was comparable to estimates of the dose from daily water ingestion. The risk associated with a single, 10-min shower was estimated to be 1.22 x 10(-4), while the estimated risk from daily ingestion of tap water ranged from 0.130 x 10(-4) to 1.80 x 10(-4) for 0.15 and 2.0 L, respectively. Since the estimates of chloroform risk from domestic water use for the three exposure routes--ingestion, inhalation, and dermal--are similar, all routes must be used to calculate the total risk when making policy decisions regarding the quality of the municipal water supply.     

Quality splitting in waste incineration due to non-convex production possibilities

Using a real case study of waste incineration, we show a new form of non-convexity in the transformation process of the inputs into the outputs. Its consequence is quality splitting, i.e. the separate use of different input qualities, yielding a better result than a homogeneous mix. For waste incineration plants (WIP), this leads to surprising practical implications for strategies of waste collection and supply, as well as for the control of a WIP. The insights are based on the evaluation of a basic model of waste incineration developed for the case study. Thus, the paper also contributes to production research by modelling waste incineration as a central process for the “reduction” of waste from manufacturing and consumption.     

Diesel Emissions and Lung Cancer1

This paper uses two different methods to assess the potential risk of human lung cancer from exposure to diesel engine emissions. One method analyzes the best available epidemiological evidence on the lung cancer risks of persons exposed in their occupations to diesel engine emissions. The second conducts a comparative analysis of laboratory and epidemiological data on diesel engine emissions and two chemically related environmental exposures–coke oven emissions and roofing tar emissions. The estimates of potential risk derived from these two distinct methods are compared. The sources of uncertainty in each method are explicitly characterized. The value of these estimates for comparing the potential lung cancer risks from exposure to diesel engine emissions with other personal and societal risks are discussed. Also considered are the limitations of these results in predicting the possible excess incidence of lung cancer from ambient exposure to diesel emissions.     

Determination of Less-Than-Lifetime Exposures to Point Source Emissions

This paper presents a method of estimating long-term exposures to point source emissions. The method consists of a Monte Carlo exposure model (PSEM or Point Source Exposure Model) that combines data on population mobility and mortality with information on daily activity patterns. The approach behind the model can be applied to a wide variety of exposure scenarios. In this paper, PSEM is used to characterize the range and distribution of lifetime equivalent doses received by inhalation of air contaminated by the emissions of a point source. The output of the model provides quantitative information on the dose, age, and gender of highly exposed individuals. The model is then used in an example risk assessment. Finally, future uses of the model's approach are discussed.     

Who Would Be Willing to Accept Disaster Debris in Their Backyard? Investigating the Determinants of Public Attitudes in Post‐Fukushima Japan

In the wake of the 2011 Great East Japan Earthquake and tsunami, the Ministry of Environment in Japan asked municipalities nationwide to accept and treat disaster waste. This call for cross‐jurisdictional waste treatment provoked considerable public controversy. To explore how the national and municipal governments can seek more public acceptance in the wake of future disasters, this study implemented a nationwide survey and addressed the question of what factors influence the public's willingness to support their municipalities’ plans to host disaster waste. Three strands of the literature—on risk perception, public dissent, and prosocial behavior—offer valuable insights into hypothesis building, although none has addressed the above question. Estimates from an ordered logistic regression (N = 1,063) reveal that the conditions of a nuclear accident and living with a small child in the household would lower the level of support for accepting disaster waste, although this does not mean that people would give their support in the absence of a nuclear accident. The results also suggest that the national and municipal governments should communicate more with the public about the risks, benefits, and costs associated with hosting disaster debris, and make efforts to improve public trust in the national government.