Exposure Assessment Procedures Research Articles

Quick Roadmap for Exposure Assessment of Contaminants in Food

The presence of chemical contaminants in food is often unavoidable and associated with many adverse health effects. Exposure assessment is the essential element of an overall risk assessment process. While the specific purpose of the exposure assessment process can vary, the main goal is to provide a foundation for health-protective decisions. In recent years, there have been significant advances in exposure assessment methodologies and procedures, subsequently contributing to an increased complexity of the process. This paper aims to provide a generalized, simplified, and practical road map for exposure assessment, pointing to the pros and cons of different methods and challenges that occur while performing this type of study.

Assessment of dermal exposure to pesticides among farmers using dosimeter and hand washing methods.

Inappropriate use of pesticides followed by unsafe handling practices to control the insect infestation among the farming groups in developing countries has resulted in a high exposure risk. The use of personal protective equipment is also negligible among Indian farmers due to their affordability to access the same. Very little research has been conducted to establish an exposure assessment procedure through dermal penetration of pesticide residues. Therefore, to quantify the contamination of pesticide residues through dermal exposure along with detailed field observations and pesticide management practices, a field study was conducted in Rangareddy district, Telangana, Southern India, to assess the dermal exposure based on dosimeter and hand washing methods. The analytical method was modified and validated in-house for performance parameters such as limit of detection, quantification, linear range, recovery, and precision. The potential dermal exposure values ranged from 0.15 to 13.45 μg, while a reduction was found in exposure levels as actual dermal exposure values ranged from 0 to 0.629 μg. Contamination through hand washing was the major contributor to overall dermal exposure. Statistical analysis revealed a significant difference in the exposed dermal regions of the leg and torso after the use of PPE. Penetration factor for each anatomical region and risk evaluation in terms of the Margin of Safety implies unsafe handling of pesticides. The findings of the present study confirm the increased exposure to organophosphate pesticides among operators and highlight the importance of the use of protective measures, especially among those that focus on dermal exposure mitigation.

Exposure Indices of Extreme Wind-Driven Rain Events for Built Heritage

Building performance and material change of cultural heritage in urban areas are negatively impacted by wind-driven rain (WDR). The frequency and intensity of WDR exposure are modified by climate change. Current approaches to exposure assessment emphasise prolonged exposure. Here, we propose indices to represent the exposure of cultural heritage to extreme WDR events. The indices are derived in two stages: (1) time-binning of long-term exposure, and (2) statistical representation of the occurrence of infrequent but intense events by fitting to the Generalised Extreme Value (GEV) distribution. A comparison to an existing exposure assessment procedure demonstrates that the proposed indices better represent shorter, more intense, and more consistent WDR events. Indices developed for seasons had greater statistical confidence than those developed for annual exposure. One index is contextualised within a model of a gutter on a terraced building: this converts the index from a measure of exposure to potential impact. This evaluation demonstrated the importance of maintenance to reduce the potential impact of WDR events. This work has direct and indirect implications for developing robust assessment procedures for cultural heritage exposure to extreme weather events.

A review of exposure assessment methods for epidemiological studies of health effects related to industrially contaminated sites.

this paper is based upon work from COST Action ICSHNet. Health risks related to living close to industrially contaminated sites (ICSs) are a public concern. Toxicology-based risk assessment of single contaminants is the main approach to assess health risks, but epidemiological studies which investigate the relationships between exposure and health directly in the affected population have contributed important evidence. Limitations in exposure assessment have substantially contributed to uncertainty about associations found in epidemiological studies. to examine exposure assessment methods that have been used in epidemiological studies on ICSs and to provide recommendations for improved exposure assessment in epidemiological studies by comparing exposure assessment methods in epidemiological studies and risk assessments. after defining the multi-media framework of exposure related to ICSs, we discussed selected multi-media models applied in Europe. We provided an overview of exposure assessment in 54 epidemiological studies from a systematic review of hazardous waste sites; a systematic review of 41 epidemiological studies on incinerators and 52 additional studies on ICSs and health identified for this review. we identified 10 multi-media models used in Europe primarily for risk assessment. Recent models incorporated estimation of internal biomarker levels. Predictions of the models differ particularly for the routes 'indoor air inhalation' and 'vegetable consumption'. Virtually all of the 54 hazardous waste studies used proximity indicators of exposure, based on municipality or zip code of residence (28 studies) or distance to a contaminated site (25 studies). One study used human biomonitoring. In virtually all epidemiological studies, actual land use was ignored. In the 52 additional studies on contaminated sites, proximity indicators were applied in 39 studies, air pollution dispersion modelling in 6 studies, and human biomonitoring in 9 studies. Exposure assessment in epidemiological studies on incinerators included indicators (presence of source in municipality and distance to the incinerator) and air dispersion modelling. Environmental multi-media modelling methods were not applied in any of the three groups of studies. recommendations for refined exposure assessment in epidemiological studies included the use of more sophisticated exposure metrics instead of simple proximity indicators where feasible, as distance from a source results in misclassification of exposure as it ignores key determinants of environmental fate and transport, source characteristics, land use, and human consumption behaviour. More validation studies using personal exposure or human biomonitoring are needed to assess misclassification of exposure. Exposure assessment should take more advantage of the detailed multi-media exposure assessment procedures developed for risk assessment. The use of indicators can be substantially improved by linking definition of zones of exposure to existing knowledge of extent of dispersion. Studies should incorporate more often land use and individual behaviour.

The role of occupational Aspergillus exposure in the development of diseases.

Aspergillus spp. have a high nutritional versatility and good growth on a large variety of construction materials. They also colonize soil or food, but decaying vegetation is their primary ecological niche. Therefore, exposure to fungi may occur at home, during hospitalization, during specific leisure activities, or at the workplace. The development of Aspergillus infections depends on the interplay between host susceptibility and the organism. Environments with high counts of fungal elements (conidia, hyphal fragments and others), high levels of bioarerosols, and elevated concentrations of mycotoxins or other volatile organic compounds should be considered as potential hazards, since they may present a risk to the exposed person. Rural tasks as well as work related to wood and food industries, poultries, swineries, waste handling plants, and other occupational environments involving contaminated organic material are among the ones posing higher respiratory risks to the workers. This paper presents a review of several studies related to occupational and indoor exposure to Aspergillus, potential health effects related to that exposure, and associated exposure assessment procedures.

Equilibrium Relationship between SVOCs in PVC Products and the Air in Contact with the Product.

Phthalates and phthalate alternatives are semivolatile organic compounds (SVOCs) present in many PVC products as plasticizers to enhance product performance. Knowledge of the mass-transfer parameters, including the equilibrium concentration in the air in contact with the product surface ( y0), will greatly improve the ability to estimate the emission rate of SVOCs from these products and to assess human exposure. The objective of this study was to measure y0 for different PVC products and to evaluate its relationship with the material-phase concentrations ( C0). Also, C0 and y0 data from other sources were included, resulting in a substantially larger data set ( Ntotal = 34, T = 25 °C) than found in previous studies. The results show that the material/gas equilibrium relationship does not follow Raoult's law and that therefore the assumption of an ideal solution is invalid. Instead, Henry's law applies, and the Henry's law constant for all target SVOCs consists of the respective pure liquid vapor pressure and an activity coefficient γ, which accounts for the nonideal nature of the solution. For individual SVOCs, a simple partitioning relationship exists, but Henry's law is more generally applicable and will be of greater value in rapid exposure assessment procedures.

Occupational exposures to leaded and unleaded gasoline engine emissions and lung cancer risk

ObjectivesTo determine whether occupational exposure to gasoline engine emissions (GEE) increased the risk of lung cancer and more specifically whether leaded or unleaded GEE increased the risk.MethodsTwo population-based case–control studies...

Toluene Diisocyanate Exposure: Exposure Assessment and Development of Cross-Facility Similar Exposure Groups Among Toluene Diisocyanate Production Plants.

The objective of this study was to characterize workplace toluene diisocyanate (TDI) exposures using standardized industrial hygiene exposure assessment procedures for use in a prospective epidemiologic study of occupational asthma. Over 2300 representative routine full shift time-weighted average (TWA) and short-term high potential exposure tasks (HPETs) air samples in groups across three TDI plants were collected over a nearly 7-year period. Data-derived similar exposure groups (SuperSEGs) were developed across the plants based on TWA sampling using cluster analysis. Individual cumulative exposure estimates were developed on the basis of the SuperSEGs. Workplace TWA exposures to TDI were adequately characterized quantitatively, but HPET exposures were adequately characterized only by qualitative measures. The mean TWA exposure was 0.65 parts per billion for 1594 routine samples. These TWA and HPET exposures can be used to support exposure-response analyses.

Water requirements and drinking rates of homing pigeons: A consideration for exposure risk of migratory birds.

Access to water along a bird's migratory flyway is essential during the vital process of migration. Because of the scarcity of water in some environments, there is potential for migratory birds to encounter and drink from contaminated bodies of water. Ingestion of contaminated water may cause injury and compromise flying ability, leading to a disruption of migration. To determine injury to birds from potential exposure, it is essential to know not only the concentration of a given contaminant in the water but also the quantity and rate of water consumption by the birds. Homing pigeons (Columba livia) were used in a series of experiments to determine differences in drinking behavior after various flights and after periods of resting. Results from the present study demonstrate that homing pigeons' water consumption is dramatically different when assessed according to activity, flight distance, and time elapsed after flight. This suggests that the drinking rates of birds during migration are extremely important and much greater than estimated using traditional exposure assessment procedures. Thus, exposure to contaminants via drinking water may be greatly underestimated, and the rate of water consumption should be considered when estimating potential exposure risk to avian species. Integr Environ Assess Manag 2017;13:870-876. © 2017 SETAC.

Extremely low gestational age and very low birthweight for gestational age are risk factors for autism spectrum disorder in a large cohort study of 10-year-old children born at 23-27 weeks’ gestation

No prospective cohort study of high-risk children has used rigorous exposure assessment and optimal diagnostic procedures to examine the perinatal antecedents of autism spectrum disorder separately among those with and without cognitive impairment. We sought to identify perinatal factors associated with increased risk for autism spectrum disorder with and without intellectual disability (intelligence quotient <70) in children born extremely preterm. This prospective multicenter (14 institutions in 5 states) birth cohort study included children born at 23-27 weeks' gestation in 2002 through 2004 who were evaluated for autism spectrum disorder and intellectual disability at age 10 years. Pregnancy information was obtained from medical records and by structured maternal interview. Cervical-vaginal "infection" refers to maternal report of bacterial infection (n= 4), bacterial vaginosis (n= 30), yeast infection (n= 62), mixed infection (n= 4), or other/unspecified infection (n= 43; eg, chlamydia, trichomonas, or herpes). We do not know the extent to which infection per se was confirmed by microbial colonization. We use the terms "fetal growth restriction" and "small for gestational age" interchangeably in light of the ongoing challenge to discern pathologically from constitutionally small newborns. Severe fetal growth restriction was defined as a birthweight Z-score for gestational age at delivery <-2 (ie, ≥2 SD below the median birthweight in a referent sample that excluded pregnancies delivered for preeclampsia or fetal indications). Participants were classified into 4 groups based on whether or not they met rigorous diagnostic criteria for autism spectrum disorder and intellectual disability (autism spectrum disorder+/intellectual disability-, autism spectrum disorder+/intellectual disability+, autism spectrum disorder-/intellectual disability+, and autism spectrum disorder-/intellectual disability-). Temporally ordered multinomial logistic regression models were used to examine the information conveyed by perinatal factors about increased risk for autism spectrum disorder and/or intellectual disability (autism spectrum disorder+/intellectual disability-, autism spectrum disorder+/intellectual disability+, and autism spectrum disorder-/intellectual disability+). In all, 889 of 966 (92%) children recruited were assessed at age 10 years, of whom 857 (96%) were assessed for autism spectrum disorder; of these, 840 (98%) children were assessed for intellectual disability. Autism spectrum disorder+/intellectual disability- was diagnosed in 3.2% (27/840), autism spectrum disorder+/intellectual disability+ in 3.8% (32/840), and autism spectrum disorder-/intellectual disability+ in 8.5% (71/840). Maternal report of presumed cervical-vaginal infection during pregnancy was associated with increased risk of autism spectrum disorder+/intellectual disability+ (odds ratio, 2.7; 95% confidence interval, 1.2-6.4). The lowest gestational age category (23-24 weeks) was associated with increased risk of autism spectrum disorder+/intellectual disability+ (odds ratio, 2.9; 95% confidence interval, 1.3-6.6) and autism spectrum disorder+/intellectual disability- (odds ratio, 4.4; 95% confidence interval, 1.7-11). Severe fetal growth restriction was strongly associated with increased risk for autism spectrum disorder+/intellectual disability- (odds ratio, 9.9; 95% confidence interval, 3.3-30), whereas peripartum maternal fever was uniquely associated with increased risk of autism spectrum disorder-/intellectual disability+ (odds ratio, 2.9; 95% confidence interval, 1.2-6.7). Our study confirms that low gestational age is associated with increased risk for autism spectrum disorder irrespective of intellectual ability, whereas severe fetal growth restriction is strongly associated with autism spectrum disorder without intellectual disability. Maternal report of cervical-vaginal infection is associated with increased risk of autism spectrum disorder with intellectual disability, and peripartum maternal fever is associated with increased risk for intellectual disability without autism spectrum disorder.

The Intersection of Care Seeking and Clinical Capacity for Patients With Highly Pathogenic Avian Influenza A (H5N1) Virus in Indonesia: Knowledge and Treatment Practices of the Public and Physicians.

Indonesia has the highest human mortality from highly pathogenic avian influenza (HPAI) A (H5N1) virus infection in the world. A survey of households (N=2520) measured treatment sources and beliefs among symptomatic household members. A survey of physicians (N=554) in various types of health care facilities measured knowledge, assessment and testing behaviors, and perceived clinical capacity. Households reported confidence in health care system capacity but infrequently sought treatment for potential HPAI H5N1 signs/symptoms. More clinicians were confident in their knowledge of diagnosis and treatment than in the adequacy of related equipment and resources at their facilities. Physicians expressed awareness of the HPAI H5N1 suspect case definition, yet expressed only moderate knowledge in questioning symptomatic patients about exposures. Self-reported likelihood of testing for HPAI H5N1 virus was high after learning of certain exposures. Knowledge of antiviral treatment was moderate, but it was higher among clinicians in puskesmas. Physicians in private outpatient clinics, the most heavily used facilities, reported the lowest confidence in their diagnostic and treatment capabilities. Educational campaigns can encourage recall of possible poultry exposure when patients are experiencing signs/symptoms and can raise awareness of the effectiveness of antivirals to drive people to seek health care. Clinicians may benefit from training regarding exposure assessment and referral procedures, particularly in private clinics. (Disaster Med Public Health Preparedness. 2016;10:838-847).

EFSA Guidance Document for predicting environmental concentrations of active substances of plant protection products and transformation products of these active substances in soil

This EFSA guidance document provides guidance for the exposure assessment of soil organisms to plant protection products (PPPs) and their transformation products in accordance with Regulation (EC) No 1107/2009 of the European Parliament and the Council. This guidance was produced by EFSA in response to a question posed by the European Commission according to Art. 31 of Regulation (EC) No 178/2002 of the European Parliament and of the Council. Guidance is provided for all types of concentrations that are potentially needed for assessing ecotoxicological effects, i.e. the concentration in total soil and the concentration in pore water, both averaged over various depths and time windows. The current guidance is restricted to annual field crops under conventional and reduced tillage. The recommended exposure assessment procedure consists of five tiers. To facilitate efficient use of the tiered approach in regulatory practice, user-friendly software tools have been developed. In higher tiers of the exposure assessment, crop interception and subsequent dissipation at the crop canopy may be included. The models that simulate these processes were harmonised. In addition, an easy-to-use table for the fraction of the dose reaching the soil has been developed, which should be used at higher tiers in combination with the simple analytical model. With respect to substance-specific model inputs, this guidance generally follows earlier documents; however, new guidance is included for some specific substance parameters.

Assessment of potential dermal and inhalation exposure of workers to the insecticide imidacloprid using whole-body dosimetry in China

In China, although improvements to the pesticide registration process have been made in last thirty years, no occupational exposure data are required to obtain a commercial license for a pesticide product. Consequently, notably little research has been conducted to establish an exposure assessment procedure in China. The present study monitored the potential dermal operator exposure from knapsack electric sprayer wheat field application of imidacloprid in Liaocheng City, Shandong Province and in Xinxiang City, Henan Province, China, using whole-body dosimetry. The potential inhalation exposure was determined using a personal air pump and XAD-2 sample tubes. The analytical method was developed and validated, including such performance parameters as limits of detection and quantification, linear range, recovery and precision. The total potential dermal and inhalation exposures were 14.20, 16.80, 15.39 and 20.78mL/hr, respectively, for the four operators in Liaocheng and Xinxiang, corresponding to 0.02% to 0.03% of the applied volume of spray solution. In all trials, the lower part (thigh, lower leg) of the body was the most contaminated, accounting for approximately 76% to 88% of the total exposure. The inhalation exposure was less than 1% of the total exposure. Such factors as the application pattern, crop type, spray equipment, operator experience and climatic conditions have been used to explain the exposure distribution over the different parts of the body. As indicated by the calculated Margin of Exposure, the typical wheat treatment scenarios when a backpack sprayer was used are considered to be safe in terms of imidacloprid exposure.

Nanopesticides: State of Knowledge, Environmental Fate, and Exposure Modeling

Published literature has been reviewed in order to (a) explore the (potential) applications of nanotechnology in pesticide formulation, (b) identify possible impacts on environmental fate, and (c) analyze the suitability of current exposure assessment procedures to account for the novel properties of nanopesticides within the EU regulatory context. The term nanopesticide covers a wide variety of products and cannot be considered to represent a single category. Many nanoformulations combine several surfactants, polymers, and metal nanoparticles in the nanometer size range. The aims of nanoformulations are generally common to other pesticide formulations, these being to increase the apparent solubility of poorly soluble active ingredients, to release the active ingredient in a slow/targeted manner and/or to protect against premature degradation. Nanoformulations are thus expected to (a) have significant impacts on the fate of active ingredients and/or (b) introduce new ingredients for which the environmental fate is still poorly understood (e.g., nanosilver). Therefore, it seems that adaptations of current exposure assessment approaches will be necessary, at least for some nanopesticides. The present analysis provides a useful framework to identify priorities for future research in order to achieve more robust risk assessments of nanopesticides.

Occupational Trichloroethylene Exposure and Kidney Cancer

We conducted a meta-analysis of occupational studies of trichloroethylene-exposed workers to evaluate patterns of associations by study design, exposure assessment methods, and occupational groups. Estimates of summary relative risk (RR) were calculated using inverse-variance weighting methods. Cohort studies were classified as group I or group II, depending on quality of the study design and exposure assessment procedures. We conducted sensitivity analyses to examine sources of heterogeneity. Across all studies meeting our inclusion criteria (n = 23), the summary RR was 1.42 (95% confidence interval = 1.17-1.77), with heterogeneity present (test for heterogeneity: P = 0.001). After removal of 3 outlier studies, the summary RR for the remaining studies was 1.24 (1.06-1.45 (test for heterogeneity: P = 0.616)). The summary RR for studies of workers who were identified as more likely exposed to trichloroethylene (group I studies) was 1.34 (1.06-1.68). With outlier studies removed, the group II summary RR estimates for the cohort studies was 0.88 (0.58-1.33) and for the case-control studies was 1.33 (1.02-1.73). The summary RR for studies that used biomarkers to classify exposure (n = 3) was 1.02 (0.59-1.77) and for studies of aerospace/aircraft workers (n = 7) was 1.14 (0.84-1.57). Positive associations were observed across various study groups. However, considerations of unmeasured potential confounding, lack of quantitative exposure assessment and lack of exposure-response patterns limit epidemiologic insight into the role of trichloroethylene exposure and its potential causal association with kidney cancer.

Exposure assessment procedures in presence of wideband digital wireless networks

The article analyses the applicability of traditional methods, as well as recently proposed techniques, to the exposure assessment of electromagnetic field generated by wireless transmitters. As is well known, a correct measurement of the electromagnetic field is conditioned by the complexity of the signal, which requires dedicated instruments or specifically developed extrapolation techniques. Nevertheless, it is also influenced by the typology of the deployment of the transmitting and receiving stations, which varies from network to network. These aspects have been intensively analysed in the literature and several cases of study are available for review. The present article collects the most recent analyses and discusses their applicability to different scenarios, typical of the main wireless networking applications: broadcasting services, mobile cellular networks and data access provisioning infrastructures.

Pentachlorophenol and Cancer Risk: Focusing the Lens on Specific Chlorophenols and Contaminants

ObjectivePentachlorophenol, a fungicide widely used as a wood preservative, was classified in 1999 by the International Agency for Research on Cancer as a possible human carcinogen. We reviewed currently available data to determine the extent to which recent studies assist in distinguishing the effect of pentachlorophenol from that of its contaminants (e.g., dioxins and other chlorophenols).Data sources and extractionWe performed a systematic review of published studies pertaining to cancer risk in relation to pentachlorophenol exposure, focusing on results pertaining specifically to all cancer sites and specific hematopoietic cancers, and data pertaining to risks associated with other types of chlorophenols, dioxins, or furans.SynthesisThe pentachlorophenol studies presented considerable evidence pertaining to hematopoietic cancers, with strong associations seen in multiple studies, in different locations, and using different designs. There is little evidence of an association between these cancers and chlorophenols that contain fewer than four chlorines. The extension of a large cohort study of sawmill workers, with follow-up to 1995, provided information about risks of relatively rare cancers (e.g., non-Hodgkin lymphoma, multiple myeloma), using a validated exposure assessment procedure that distinguishes between exposures to pentachlorophenol and tetrachlorophenol. In contrast with dioxin, pentachlorophenol exposure has not been associated with total cancer incidence or mortality.ConclusionsThe updated cohort study focusing on pentachlorophenol provides increased statistical power and precision, and demonstrates associations between hematopoietic cancer and pentachlorophenol exposure not observed in earlier evaluations of this cohort. Contaminant confounding is an unlikely explanation for the risks seen with pentachlorophenol exposure.

Issues in consumer exposure modeling: Towards harmonization on a global scale

Understanding where and how chemicals are used throughout their life cycle is becoming increasingly important. In 2003, within the context of REACH and GPSD legislation, the European Commission started developing a European and global infrastructure of exposure methods and tools. The infrastructure aims (1) to link modeling tools and exposure-related data and scenarios in a single framework so that harmonized exposure assessment procedures can be developed for consumer products in the EU and (2) to make this framework flexible enough to allow global application. A number of issues are raised by a global infrastructure of consumer exposure modeling that answers to multi-legislative mandates. These include transparency, consistency, usability, and defensibility of the models, including the relevant degree of complexity for priority setting versus assessment. As part of the initiative to set up a harmonized global infrastructure on consumer exposure assessment, these issues were presented, discussed, and further developed in a series of European Commission-sponsored workshops organized in October 2004 and June 2005 as part of the "Harmonization of Consumer Exposure Models on a Global Scale" project. The project focused on development, harmonization, and validation of consumer exposure modeling approaches. The workshops included experts from the EU, USA, Japan, and Canada. The conclusions and recommendations made on the basis of this work are described. To help achieve harmonization of approaches, the European Commission's Joint Research Centre is proposing a framework (1) to compare information on elements of chemical risk assessment to understand exposure regulations in different countries, (2) to save time and expense by sharing information and models, and (3) to promote credible science through better communication among organizations and by peer review of assessments and assessment procedures.

Toward Harmonization of Dermal Absorption Methods for Environmental Health Exposure Assessment

MM2-O-07 Dermal contact with chemically contaminated water and soil may be an important route of exposure. Water and soil can be contaminated directly as a result of chemical application and spills or indirectly as a result of surface water runoff or erosion. Individuals may be exposed by playing or working in contaminated water or soil. Currently, reliable information is lacking about dermal contact with chemically contaminated water and soil making it difficult to accurately estimate dermal exposure and risk in these situations. Models that attempt to predict dermal contact and penetration are based on limited data with little validation. This condition results in confusion and debate about the magnitude of public health risks associated with dermal exposure and the measures required for regulation. We are engaged in investigations to identify the chemical and physical properties of soil that affect chemical movement from soil to skin and development of a mechanistic model for dermal absorption of contaminants in soil. Additional work is being conducted to evaluate in vitro dermal absorption test methods and to generate guidance to validate them. Our results show that differences in dermal absorption estimates reported in the literature are largely due to contaminant loading procedures and to choice of solvent for receptor fluids. Review of dermal exposure assessment procedures across the Agency is being conducted to ascertain similarities and differences in measurement methods with the intent to harmonize them to the extent possible. Collectively, we anticipate these efforts will improve the precision and accuracy of dermal exposure assessment methods and improve our understanding about the significance of the dermal route of exposure. The opinions expressed in this manuscript are those of the author and do not reflect opinions or policy of the Environmental Protection Agency. Mention of trade names or commercial products does not constitute an endorsement or recommendation for use.

Assessment of exposure in an international study on cancer risks among pulp, paper, and paper product workers.

A data management system and a department-exposure matrix (PAPDEM) was designed and constructed to facilitate exposure assessment for a large multinational study on cancer risks among pulp, paper, and paper product workers. Exposure to 25 major agents was described by prevalence, P (i.e., proportion of the exposed, classified %-range), and level, L (i.e., annual mean concentration at work, classified). Some agents could be assessed only in qualitative terms. The assessment was specific to mill, work department, agent, and time period. The results of industrial hygiene measurements, information from detailed company questionnaires, and the professional judgments of the assessment team were the cornerstones of the assessment. Validity and consistency of the assessment were aimed at by setting default values for P and L prior to the assessment, accurately defining agents and exposure classes, dividing assessment work by subindustry, working in pairs, testing interrater agreement, and finalizing the estimates in a meeting. In spite of these precautions, good agreement between different assessors was difficult to reach. Exposure to chemical agents turned out to be widespread and complex with frequent multiple exposures. A computer-assisted exposure assessment system such as PAPDEM may save time and facilitate assessment in large epidemiological studies requiring complicated exposure assessment procedures. It also provides a good documentation of exposure assignments, which may be useful in the interpretation of the results and in future updates of the study.