Exposure science: a view of the past and milestones for the future

Cutting-edge computational chemical exposure research at the U.S. Environmental Protection Agency

Exposure science is evolving from its traditional "after the fact" and "one chemical at a time" approach to forecasting chemical exposures rapidly enough to keep pace with the constantly expanding landscape of chemicals and exposures. In this article, we provide an overview of the approaches, accomplishments, and plans for advancing computational exposure science within the U.S. Environmental Protection Agency's Office of Research and Development (EPA/ORD). First, to characterize the universe of chemicals in commerce and the environment, a carefully curated, web-accessible chemical resource has been created. This DSSTox database unambiguously identifies >1.2 million unique substances reflecting potential environmental and human exposures and includes computationally accessible links to each compound's corresponding data resources. Next, EPA is developing, applying, and evaluating predictive exposure models. These models increasingly rely on data, computational tools like quantitative structure activity relationship (QSAR) models, and machine learning/artificial intelligence to provide timely and efficient prediction of chemical exposure (and associated uncertainty) for thousands of chemicals at a time. Integral to this modeling effort, EPA is developing data resources across the exposure continuum that includes application of high-resolution mass spectrometry (HRMS) non-targeted analysis (NTA) methods providing measurement capability at scale with the number of chemicals in commerce. These research efforts are integrated and well-tailored to support population exposure assessment to prioritize chemicals for exposure as a critical input to risk management. In addition, the exposure forecasts will allow a wide variety of stakeholders to explore sustainable initiatives like green chemistry to achieve economic, social, and environmental prosperity and protection of future generations.

Beyond heat exposure - new methods to quantify and link personal heat exposure, stress, and strain in diverse populations and climates: The journal Temperature toolbox

Fine-scale personal heat exposure (PHE) information can help prevent or minimize weather-related deaths, illnesses, and reduced work productivity. Common methods to estimate heat risk do not simultaneously account for the intensity, frequency, and duration of thermal exposures, nor do they include inter-individual factors that modify physiological response. This study demonstrates new whole-body net thermal load estimations to link PHE to heat stress and strain over time. We apply a human-environment heat exchange model to examine how time-varying net thermal loads differ across climate contexts, personal attributes, and spatiotemporal scales. First, we investigate summertime climatic PHE impacts for three US cities: Phoenix, Miami, and New York. Second, we model body morphology and acclimatization for three profiles (middle-aged male/female; female >65 years). Finally, we quantify model sensitivity using representative data at synoptic and micro-scales. For all cases, we compare required and potential evaporative heat losses that can lead to dangerous thermal exposures based on (un)compensable heat stress. Results reveal misclassifications in heat stress or strain due to incomplete environmental data and assumed equivalent physiology and activities between people. Heat strain is most poorly represented by PHE alone for the elderly, non-acclimatized, those engaged in strenuous activities, and when negating solar radiation. Moreover, humid versus dry heat across climates elicits distinct thermal responses from the body. We outline criteria for inclusive PHE evaluations connecting heat exposure, stress, and strain while using physiological-based methods to avoid misclassifications. This work underlines the value of moving from "one-size-fits-all" thermal indices to "fit-for-purpose" approaches using personalized information.

A SWOT analysis of contemporary gaps and a possible diagnostic tool for environmental health in an upper-middle income country: a case study of South Africa

This study evaluated the state of environmental health in the Republic of South Africa using the strengths, weaknesses, opportunities, and threats (SWOT) analysis framework. The internal and external factor evaluations were conducted by reviewing existing literature searched using a combination of keywords and boolean functions. The weighted score for the strengths and weaknesses was 0.79 and 1.04, respectively. The external factor evaluations findings revealed that environmental health has an equal amount of threats and opportunities, however, the threats outweigh the opportunities. The total weighted score for the internal and external factor evaluations was 1.83 and 2.25, respectively, which were below the average value of 2.5. The internal-external factors matrix indicated that environmental health in the Republic of South Africa needs to be refocused and re-aligned to public health protection. Failure to address the weaknesses and threats and optimise the strengths and opportunities may further weaken the provision of environmental health services.

Framework for developing an exposure science curriculum as part of the European Exposure Science Strategy 2020-2030

BACKGROUND

Evaluating and managing exposures to chemical, physical and biological stressors, which frequently interplay with psychological stressors as well as social and behavioural aspects, is crucial for protecting human and environmental health and transitioning towards a sustainable future. Advances in our understanding of exposure rely on input from well-trained exposure scientists. However, no education programmes in Europe are currently explicitly dedicated to cover the broader range of exposure science approaches, applications, stressors and receptors.

OBJECTIVE

To address this challenge, a curriculum is needed that yields credible, well-defined career pathways in exposure science.

METHODS

Needs and conditions for advancing exposure science education in Europe were identified. As a starting point for a way forward, harmonised learning outcomes for exposure science were defined at each level of the European Qualifications Framework. The course programme coordinators were recruited for three varying courses, with respect to the course level and the proportion of the curriculum dedicated to exposure science. These courses were assessed via our systematic course review procedure. Finally, strategic objectives and actions are proposed to build exposure science education programmes.

RESULTS

The ISES Europe 'Education, Training and Communication' expert working group developed a framework for creating a viable exposure science curriculum. Harmonised learning outcomes were structured under eight learning levels, categorised by knowledge, skills and competence. Illustrative case studies demonstrated how education providers integrated these learning outcomes for their educational context and aligned the overall exposure science curriculum.

CONCLUSIONS

The international recognition and adoption of exposure science education will enable advances in addressing global exposure science challenges for various stressors, from behavioural aspects from individual to population scale, and effective communication between exposure scientists and relevant stakeholders and policy makers, as part of the European Exposure Science Strategy 2020-2030.

Effect of indoor and outdoor sources on indoor particle concentrations in South Korean residential buildings

The rising indoor air pollution from particles is a cause for concern especially in houses where children and the elderly reside. In South Korea, assessment of exposure to particle number (PN) in residential apartments, which account for 76% of all houses, is limited. In our study, the indoor and outdoor PN (sizes 0.3-10.0 µm) concentrations were measured in ten typical apartments for 24 h each. In addition, the occupants' schedules were examined by conducting a survey. Results showed that the average outdoor PN concentrations were 0.30-4.37 × 10⁹/m³ with very large deviations. Indoor peak events were mainly caused by cooking, and total emitted particles were 0.01-81.3 × 10¹³ particles. Indoor PN concentrations were sustained for a long time because of inefficient ventilation that led to lowered attenuation. Indoor particles are generated during various indoor activities. The daily-integrated particle exposures were 21.4% and 78.6% for indoor and outdoor sources, respectively. Thus, outdoor sources were the predominant sources of particle exposure compared with indoor sources. In conclusion, penetration from outdoor sources needs to be reduced by adding air filtration to improve the airtightness of buildings when introducing outdoor air to lower the indoor PN concentration.

Environmental exposure during travel: A research review and suggestions forward

Daily travel through the urban fabric exposes urban dwellers to a range of environmental conditions that may have an impact on their health and wellbeing. Knowledge about exposures during travel, their associations with travel behavior, and their social and health outcomes are still limited. In our review, we aim to explain how the current environmental exposure research addresses the interactions between human and environmental systems during travel through their spatial, temporal and contextual dimensions. Based on the 104 selected studies, we identify significant recent advances in addressing the spatiotemporal dynamics of exposure during travel. However, the conceptual and methodological framework for understanding the role of multiple environmental exposures in travel environments is still in an early phase, and the health and wellbeing impacts at individual or population level are not well known. Further research with greater geographical balance is needed to fill the gaps in the empirical evidence, and linking environmental exposures during travel with the causal health and wellbeing outcomes. These advancements can enable evidence-based urban and transport planning to take the next step in advancing urban livability.

Measuring Environmental Exposure to Enteric Pathogens in Low-Income Settings: Review and Recommendations of an Interdisciplinary Working Group

Infections with enteric pathogens impose a heavy disease burden, especially among young children in low-income countries. Recent findings from randomized controlled trials of water, sanitation, and hygiene interventions have raised questions about current methods for assessing environmental exposure to enteric pathogens. Approaches for estimating sources and doses of exposure suffer from a number of shortcomings, including reliance on imperfect indicators of fecal contamination instead of actual pathogens and estimating exposure indirectly from imprecise measurements of pathogens in the environment and human interaction therewith. These shortcomings limit the potential for effective surveillance of exposures, identification of important sources and modes of transmission, and evaluation of the effectiveness of interventions. In this review, we summarize current and emerging approaches used to characterize enteric pathogen hazards in different environmental media as well as human interaction with those media (external measures of exposure), and review methods that measure human infection with enteric pathogens as a proxy for past exposure (internal measures of exposure). We draw from lessons learned in other areas of environmental health to highlight how external and internal measures of exposure can be used to more comprehensively assess exposure. We conclude by recommending strategies for advancing enteric pathogen exposure assessments.

Environmental Health Surveillance System for a Population Using Advanced Exposure Assessment

Human exposure to air pollution is a major public health concern. Environmental policymakers have been implementing various strategies to reduce exposure, including the 10th-day-no-driving system. To assess exposure of an entire population of a community in a highly polluted area, pollutant concentrations in microenvironments and population time–activity patterns are required. To date, population exposure to air pollutants has been assessed using air monitoring data from fixed atmospheric monitoring stations, atmospheric dispersion modeling, or spatial interpolation techniques for pollutant concentrations. This is coupled with census data, administrative registers, and data on the patterns of the time-based activities at the individual scale. Recent technologies such as sensors, the Internet of Things (IoT), communications technology, and artificial intelligence enable the accurate evaluation of air pollution exposure for a population in an environmental health context. In this study, the latest trends in published papers on the assessment of population exposure to air pollution were reviewed. Subsequently, this study proposes a methodology that will enable policymakers to develop an environmental health surveillance system that evaluates the distribution of air pollution exposure for a population within a target area and establish countermeasures based on advanced exposure assessment.

What Is New about the Exposome? Exploring Scientific Change in Contemporary Epidemiology

In this commentary, I discuss the scientific changes brought by the exposome, asking what is new about this approach and line of research. I place the exposome in a historical perspective, by analyzing the conditions under which the exposome has been conceived, developed and established in the context of contemporary epidemiological research. I argue that the exposome has been developed by transferring approaches, methods and conceptualizations from other lines of research in the life and health sciences. I thus discuss the conceptual and methodological innovations of the exposome as a result of the merging and adaptation of these elements for new uses and purposes. On this basis, I argue that the novelty of the exposome should be seen in incremental rather than revolutionary terms and, in this sense, the exposome shares significant elements with other projects and repertoires in postgenomics. I conclude by discussing the consequences of this analysis for the potential limitations and future development of exposome research.

Identifying predictors of personal exposure to air temperature in peri-urban India

Characterizing personal exposure to air temperature is critical to understanding exposure measurement error in epidemiologic studies using fixed-site exposure data and to identify strategies to protect public health. To date, no study evaluating personal air temperature in the general population has been conducted in a low-and-middle income country. We used data from the CHAI study consisting of 50 adults monitored in up to six non-consecutive 24 h sessions in peri-urban south India. We quantified the agreement and association between fixed-site ambient and personal air temperature, and identified predictors of personal air temperature based on housing assessment, self-reported, GPS, remote sensing, and wearable camera data. Mean (SD) daytime (6 am-10 pm) average personal air temperature was 31.2 (2.6) °C and mean nighttime (10 pm-6 am) average temperature was 28.8 (2.8) °C. Agreement between average personal air and fixed-site ambient temperatures was limited, especially at night when personal air temperatures were underestimated by fixed-site temperatures (MBE = -5.6 °C). The proportion of average personal nighttime temperature variability explained by ambient fixed-site temperatures was moderate (R²_mar = 0.39); daytime associations were stronger for women (R²_mar = 0.51) than for men (R²_mar = 0.3). Other predictors of average nighttime personal air temperature included residential altitude, ceiling height, and household income. Predictors of average daytime personal air temperature included roof materials, GPS-tracked altitude, time working in agriculture (for women), and time travelling (for men). No biomass cooking, urban heat island, or greenspace effects were identified. R²_mar between ambient fixed-site and personal air temperature indicate that ambient fixed-site temperature is only a moderately useful proxy of personal air temperature in the context of peri-urban India. Our findings suggest that people living in houses at lower altitude, with lower ceiling height and asbestos roofing sheets might be more vulnerable to heat. We also identified households with higher income, women working in agriculture and men with long commutes as disproportionately exposed to high temperatures.

Dynamic Estimation of Individual Exposure Levels to Air Pollution Using Trajectories Reconstructed from Mobile Phone Data

The spatiotemporal variability in air pollutant concentrations raises challenges in linking air pollution exposure to individual health outcomes. Thus, understanding the spatiotemporal patterns of human mobility plays an important role in air pollution epidemiology and health studies. With the advantages of massive users, wide spatial coverage and passive acquisition capability, mobile phone data have become an emerging data source for compiling exposure estimates. However, compared with air pollution monitoring data, the temporal granularity of mobile phone data is not high enough, which limits the performance of individual exposure estimation. To mitigate this problem, we present a novel method of estimating dynamic individual air pollution exposure levels using trajectories reconstructed from mobile phone data. Using the city of Shanghai as a case study, we compared three different types of exposure estimates using (1) reconstructed mobile phone trajectories, (2) recorded mobile phone trajectories, and (3) residential locations. The results demonstrate the necessity of trajectory reconstruction in exposure and health risk assessment. Additionally, we measure the potential health effects of air pollution from both individual and geographical perspectives. This helped reveal the temporal variations in individual exposures and the spatial distribution of residential areas with high exposure levels. The proposed method allows us to perform large-area and long-term exposure estimations for a large number of residents at a high spatiotemporal resolution, which helps support policy-driven environmental actions and reduce potential health risks.

A Quantitative Source-to-Outcome Case Study To Demonstrate the Integration of Human Health and Ecological End Points Using the Aggregate Exposure Pathway and Adverse Outcome Pathway Frameworks

Exposure to environmental contaminants can lead to adverse outcomes in both human and nonhuman receptors. The Aggregate Exposure Pathway (AEP) and Adverse Outcome Pathway (AOP) frameworks can mechanistically inform cumulative risk assessment for human health and ecological end points by linking together environmental transport and transformation, external exposure, toxicokinetics, and toxicodynamics. This work presents a case study of a hypothetical contaminated site to demonstrate a quantitative approach for implementing the AEP framework and linking this framework to AOPs. We construct an AEP transport and transformation model and then quantify external exposure pathways for humans, fishes, and small herbivorous mammals at the hypothetical site. A Monte Carlo approach was used to address parameter variability. Source apportionment was quantified for each species, and published pharmacokinetic models were used to estimate internal target site exposure from external exposures. Published dose-response data for a multispecies AOP network were used to interpret AEP results in the context of species-specific effects. This work demonstrates (1) the construction, analysis, and application of a quantitative AEP model, (2) the utility of AEPs for organizing mechanistic exposure data and highlighting data gaps, and (3) the advantages provided by a source-to-outcome construct for leveraging exposure data and to aid transparency regarding assumptions.

Assessing personal exposure to PM using data from an integrated indoor-outdoor experiment in Athens-Greece

An integrated indoor-outdoor 15-day PM sampling campaign in a general area close to the centre of Athens, targeted to examine personal exposure. All microenvironments (MEs) (second and fourth floor flats, cafes, cars, restaurants, underground metro, outdoor etc.) frequented by the residents were included in the study. The instrumentation used was both stationary (low volume samplers) and portable/wearable to be able to measure continuously PM₁₀, PM_2.5, PM₁ and analyze chemically PM_2.5 and PM₁ samples. The study showed that the residences' air quality was determined by the type and intensity of outdoor sources and their vertical distance from the street. Indoor activities such as cooking, cleaning further increased PM levels and formulated the air quality, while particulate accumulation was evident. In general, PM_2.5 concentrations were higher outdoors, 11-43 μg/m³, than in the second floor flat as well as on days within different MEs, 13-33 μg/m³ and 8-35 μg/m³, respectively and finally in the fourth floor 10-18 μg/m³. PM_2.5 chemical composition was typical of a Mediterranean urban area predominantly composed on average of OC/EC (33%), sulfate (13%), ammonium (9%), nitrate (5%) and crustal material (Cl-, Na⁺, K⁺, Mg²⁺ and Ca²⁺) (5%). On days when other MEs were visited crustal material increased on average to 16%. The PM levels measured with the portable instrumentation at all mEs showed that the persons were exposed to higher PM₁₀ concentrations in the subway (avg. 218 μg/m³) due to the resuspension of crustal material, while maximum PM_2.5 and PM₁ were experienced in cafes where smoking was allowed (avg. 126 and 108 μg/m³, respectively). Using the car resulted to the lowest PM₁₀, PM_2.5 and PM₁ exposure (58, 10 and 6 μg/m³, respectively). Total exposure to particulates depended both on the time spent in each ME and on the mixture of MEs visited in 24 h.

Soot and the city: Evaluating the impacts of Clean Heat policies on indoor/outdoor air quality in New York City apartments

New York City has had a long history of implementing local policies to reduce air pollution. Enacted as a part of PlaNYC, the Clean Heat policies aim to lower wintertime ambient air pollution by phasing out dirty No. 6 heating fuel oil and transitioning to comparatively cleaner No. 4, No. 2, or natural gas. This study evaluates the impacts of policies on ambient air pollution and, given that people spend the majority of their time inside, importantly, indoor air pollution. Using a natural experiment, we evaluate the effects of the policies by measuring average two-week levels of indoor and outdoor black carbon (BC) and fine particulate matter (PM2.5) in 48 upper Manhattan apartments in successive winter heating seasons before and after mandated fuel transition. We failed to observe systematic improvements in indoor BC and PM2.5 concentrations in follow-up. However, outdoor levels of PM2.5 did improve, with statistical differences observed among buildings converting to the cleanest fuels. Non-statistical improvements were observed for outdoor BC. However, when accounting for meteorological differences, apartment characteristics, and behavioral patterns that may have influenced air pollution measurements, these differences were not significant. The study results have important policy and equity implications considering the differential improvements in air quality by conversion to No. 4 oil as compared to the cleaner No. 2 oil and natural gas.

Source reconstruction of airborne toxics based on acute health effects information

The intentional or accidental release of airborne toxics poses great risk to the public health. During these incidents, the greatest factor of uncertainty is related to the location and rate of released substance, therefore, an information of high importance for emergency preparedness and response plans. A novel computational algorithm is proposed to estimate, efficiently, the location and release rate of an airborne toxic substance source based on health effects observations; data that can be readily available, in a real accident, contrary to actual measurements. The algorithm is demonstrated by deploying a semi-empirical dispersion model and Monte Carlo sampling on a simplified scenario. Input data are collected at varying receptor points for toxics concentrations (C; standard approach) and two new types: toxic load (TL) and health effects (HE; four levels). Estimated source characteristics are compared with scenario values. The use of TL required the least number of receptor points to estimate the release rate, and demonstrated the highest probability (>90%). HE required more receptor points, than C, but with lesser deviations while probability was comparable, if not better. Finally, the algorithm assessed very accurately the source location when using C and TL with comparable confidence, but HE demonstrated significantly lower confidence.

Development and evaluation of an ultrasonic personal aerosol sampler

Assessing personal exposure to air pollution has long proven challenging due to technological limitations posed by the samplers themselves. Historically, wearable aerosol monitors have proven to be expensive, noisy, and burdensome. The objective of this work was to develop a new type of wearable monitor, an ultrasonic personal aerosol sampler (UPAS), to overcome many of the technological limitations in personal exposure assessment. The UPAS is a time-integrated monitor that features a novel micropump that is virtually silent during operation. A suite of onboard environmental sensors integrated with this pump measure and record mass airflow (0.5-3.0 L/min, accurate within 5%), temperature, pressure, relative humidity, light intensity, and acceleration. Rapid development of the UPAS was made possible through recent advances in low-cost electronics, open-source programming platforms, and additive manufacturing for rapid prototyping. Interchangeable cyclone inlets provided a close match to the EPA PM_2.5 mass criterion (within 5%) for device flows at either 1.0 or 2.0 L/min. Battery life varied from 23 to 45 hours depending on sample flow rate and selected filter media. Laboratory tests of the UPAS prototype demonstrate excellent agreement with equivalent federal reference method samplers for gravimetric analysis of PM_2.5 across a broad range of concentrations.

Use of the "Exposome" in the Practice of Epidemiology: A Primer on -Omic Technologies

The exposome has been defined as the totality of exposures individuals experience over the course of their lives and how those exposures affect health. Three domains of the exposome have been identified: internal, specific external, and general external. Internal factors are those that are unique to the individual, and specific external factors include occupational exposures and lifestyle factors. The general external domain includes sociodemographic factors such as educational level and financial status. Eliciting information on the exposome is daunting and not feasible at present; the undertaking may never be fully realized. A variety of tools have been identified to measure the exposome. Biomarker measurements will be one of the major tools in exposomic studies. However, exposure data can also be obtained from other sources such as sensors, geographic information systems, and conventional tools such as survey instruments. Proof-of-concept studies are being conducted that show the promise of exposomic investigation and the integration of different kinds of data. The inherent value of exposomic data in epidemiologic studies is that they can provide greater understanding of the relationships among a broad range of chemical and other risk factors and health conditions and ultimately lead to more effective and efficient disease prevention and control.

Preparedness and response to chemical and biological threats: the role of exposure science

There are multiple components to emergency preparedness and the response to chemical and biological threat agents. The 5Rs framework (rescue, reentry, recovery, restoration, and rehabitation) outlines opportunities to apply exposure science in emergency events. Exposure science provides guidance and refined tools for characterizing, assessing, and reducing risks from catastrophic events, such as the release of hazardous airborne chemicals or biological agents. Important challenges to be met include deployment of assets, including medications, before and after an emergency response situation. Assessment of past studies demonstrates the value of integrating exposure science methods into risk analysis and the management of catastrophic events.

Considering new methodologies in strategies for safety assessment of foods and food ingredients

Toxicology and safety assessment are changing and require new strategies for evaluating risk that are less depending on apical toxicity endpoints in animal models and relying more on knowledge of the mechanism of toxicity. This manuscript describes a number of developments that could contribute to this change and implement this in a stepwise roadmap that can be applied for the evaluation of food and food ingredients. The roadmap was evaluated in four case studies by using literature and existing data. This preliminary evaluation was shown to be useful. However, this experience should be extended by including examples where experimental work needs to be included. To further implement these new insights in toxicology and safety assessment for the area of food and food ingredients, the recommendation is that stakeholders take action in addressing gaps in our knowledge, e.g. with regard to the applicability of the roadmap for mixtures and food matrices. Further development of the threshold of toxicological concern is needed, as well as cooperation with other sectors where similar schemes are under development. Moreover, a more comprehensive evaluation of the roadmap, also including the identification of the need for in vitro experimental work is recommended.

Blood-borne biomarkers and bioindicators for linking exposure to health effects in environmental health science

Environmental health science aims to link environmental pollution sources to adverse health outcomes to develop effective exposure intervention strategies that reduce long-term disease risks. Over the past few decades, the public health community recognized that health risk is driven by interaction between the human genome and external environment. Now that the human genetic code has been sequenced, establishing this "G × E" (gene-environment) interaction requires a similar effort to decode the human exposome, which is the accumulation of an individual's environmental exposures and metabolic responses throughout the person's lifetime. The exposome is composed of endogenous and exogenous chemicals, many of which are measurable as biomarkers in blood, breath, and urine. Exposure to pollutants is assessed by analyzing biofluids for the pollutant itself or its metabolic products. New methods are being developed to use a subset of biomarkers, termed bioindicators, to demonstrate biological changes indicative of future adverse health effects. Typically, environmental biomarkers are assessed using noninvasive (excreted) media, such as breath and urine. Blood is often avoided for biomonitoring due to practical reasons such as medical personnel, infectious waste, or clinical setting, despite the fact that blood represents the central compartment that interacts with every living cell and is the most relevant biofluid for certain applications and analyses. The aims of this study were to (1) review the current use of blood samples in environmental health research, (2) briefly contrast blood with other biological media, and (3) propose additional applications for blood analysis in human exposure research.

Indoor air sampling for fine particulate matter and black carbon in industrial communities in Pittsburgh

Impacts of industrial emissions on outdoor air pollution in nearby communities are well-documented. Fewer studies, however, have explored impacts on indoor air quality in these communities. Because persons in northern climates spend a majority of their time indoors, understanding indoor exposures, and the role of outdoor air pollution in shaping such exposures, is a priority issue. Braddock and Clairton, Pennsylvania, industrial communities near Pittsburgh, are home to an active steel mill and coke works, respectively, and the population experiences elevated rates of childhood asthma. Twenty-one homes were selected for 1-week indoor sampling for fine particulate matter (PM2.5) and black carbon (BC) during summer 2011 and winter 2012. Multivariate linear regression models were used to examine contributions from both outdoor concentrations and indoor sources. In the models, an outdoor infiltration component explained 10 to 39% of variability in indoor air pollution for PM2.5, and 33 to 42% for BC. For both PM2.5 models and the summer BC model, smoking was a stronger predictor than outdoor pollution, as greater pollutant concentration increases were identified. For winter BC, the model was explained by outdoor pollution and an open windows modifier. In both seasons, indoor concentrations for both PM2.5 and BC were consistently higher than residence-specific outdoor concentration estimates. Mean indoor PM2.5 was higher, on average, during summer (25.8±22.7 μg/m3) than winter (18.9±13.2 μg/m3). Contrary to the study's hypothesis, outdoor concentrations accounted for only little to moderate variability (10 to 42%) in indoor concentrations; a much greater proportion of PM2.5 was explained by cigarette smoking. Outdoor infiltration was a stronger predictor for BC compared to PM2.5, especially in winter. Our results suggest that, even in industrial communities of high outdoor pollution concentrations, indoor activities--particularly cigarette smoking--may play a larger role in shaping indoor exposures.

Uncertainties in human health risk assessment of environmental contaminants: A review and perspective

Addressing uncertainties in human health risk assessment is a critical issue when evaluating the effects of contaminants on public health. A range of uncertainties exist through the source-to-outcome continuum, including exposure assessment, hazard and risk characterisation. While various strategies have been applied to characterising uncertainty, classical approaches largely rely on how to maximise the available resources. Expert judgement, defaults and tools for characterising quantitative uncertainty attempt to fill the gap between data and regulation requirements. The experiences of researching 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) illustrated uncertainty sources and how to maximise available information to determine uncertainties, and thereby provide an 'adequate' protection to contaminant exposure. As regulatory requirements and recurring issues increase, the assessment of complex scenarios involving a large number of chemicals requires more sophisticated tools. Recent advances in exposure and toxicology science provide a large data set for environmental contaminants and public health. In particular, biomonitoring information, in vitro data streams and computational toxicology are the crucial factors in the NexGen risk assessment, as well as uncertainties minimisation. Although in this review we cannot yet predict how the exposure science and modern toxicology will develop in the long-term, current techniques from emerging science can be integrated to improve decision-making.

Assessment of phthalates/phthalate alternatives in children's toys and childcare articles: Review of the report including conclusions and recommendation of the Chronic Hazard Advisory Panel of the Consumer Product Safety Commission

The Consumer Product Safety Commission (CPSC) convened a Chronic Hazard Advisory Panel (CHAP) on Phthalates found in children's toys, and childcare products, and in products used by women of childbearing age. The CHAP conducted a risk assessment on phthalates and phthalate substitutes, and made recommendations to either ban, impose an interim ban, or allow the continued use of phthalates and phthalate substitutes in the above products. After a review of the literature, the evaluation included toxic end points of primary concern, biomonitoring results, extant exposure reconstruction, and epidemiological results. The health end points chosen were associated with the rat phthalate syndrome, which is characterized by malformations of the epididymis, vas deferens, seminal vesicles, prostate, external genitalia (hypospadias), and by cryptorchidism (undescended testes), retention of nipples/areolae, and demasculinization (~incomplete masculinization) of the perineum, resulting in reduced anogenital distance. Risk assessment demonstrated that some phthalates should be permanently banned, removed from the banned list, or remain interim banned. Biomonitoring and toxicology data provided the strongest basis for a mixture risk assessment. In contrast, external exposure data were the weakest and need to be upgraded for epidemiological studies and risk assessments. Such studies would focus on routes and sources. The review presents recommendations and uncertainties.

Commentary on the contributions and future role of occupational exposure science in a vision and strategy for the discipline of exposure science

Exposure science is a holistic concept without prejudice to exposure source. Traditionally, measurements aimed at mitigating environmental exposures have not included exposures in the workplace, instead considering such exposures to be an internal affair between workers and their employers. Similarly, occupational (or industrial) hygiene has not typically accounted for environmental contributions to poor health at work. Many persons spend a significant amount of their lifetime in the workplace, where they maybe exposed to more numerous chemicals at higher levels than elsewhere in their environment. In addition, workplace chemical exposures and other exogenous stressors may increase epigenetic and germline modifications that are passed on to future generations. We provide a brief history of the development of exposure science from its roots in the assessment of workplace exposures, including an appendix where we detail current resources for education and training in exposure science offered through occupational hygiene organizations. We describe existing successful collaborations between occupational and environmental practitioners in the field of exposure science, which may serve as a model for future interactions. Finally, we provide an integrated vision for the field of exposure science, emphasizing interagency collaboration, the need for complete exposure information in epidemiological studies, and the importance of integrating occupational, environmental, and residential assessments. Our goal is to encourage communication and spur additional collaboration between the fields of occupational and environmental exposure assessment. Providing a more comprehensive approach to exposure science is critical to the study of the "exposome", which conceptualizes the totality of exposures throughout a person's life, not only chemical, but also from diet, stress, drugs, infection, and so on, and the individual response.

Aggregate Exposure and Cumulative Risk Assessment--Integrating Occupational and Non-occupational Risk Factors

Occupational exposure limits have traditionally focused on preventing morbidity and mortality arising from inhalation exposures to individual chemical stressors in the workplace. While central to occupational risk assessment, occupational exposure limits have limited application as a refined disease prevention tool because they do not account for all of the complexities of the work and non-occupational environments and are based on varying health endpoints. To be of greater utility, occupational exposure limits and other risk management tools could integrate broader consideration of risks from multiple exposure pathways and routes (aggregate risk) as well as the combined risk from exposure to both chemical and non-chemical stressors, within and beyond the workplace, including the possibility that such exposures may cause interactions or modify the toxic effects observed (cumulative risk). Although still at a rudimentary stage in many cases, a variety of methods and tools have been developed or are being used in allied risk assessment fields to incorporate such considerations in the risk assessment process. These approaches, which are collectively referred to as cumulative risk assessment, have potential to be adapted or modified for occupational scenarios and provide a tangible path forward for occupational risk assessment. Accounting for complex exposures in the workplace and the broader risks faced by the individual also requires a more complete consideration of the composite effects of occupational and non-occupational risk factors to fully assess and manage worker health problems. Barriers to integrating these different factors remain, but new and ongoing community-based and worker health-related initiatives may provide mechanisms for identifying and integrating risk from aggregate exposures and cumulative risks from all relevant sources, be they occupational or non-occupational.

The public health exposome: a population-based, exposure science approach to health disparities research

The lack of progress in reducing health disparities suggests that new approaches are needed if we are to achieve meaningful, equitable, and lasting reductions. Current scientific paradigms do not adequately capture the complexity of the relationships between environment, personal health and population level disparities. The public health exposome is presented as a universal exposure tracking framework for integrating complex relationships between exogenous and endogenous exposures across the lifespan from conception to death. It uses a social-ecological framework that builds on the exposome paradigm for conceptualizing how exogenous exposures "get under the skin". The public health exposome approach has led our team to develop a taxonomy and bioinformatics infrastructure to integrate health outcomes data with thousands of sources of exogenous exposure, organized in four broad domains: natural, built, social, and policy environments. With the input of a transdisciplinary team, we have borrowed and applied the methods, tools and terms from various disciplines to measure the effects of environmental exposures on personal and population health outcomes and disparities, many of which may not manifest until many years later. As is customary with a paradigm shift, this approach has far reaching implications for research methods and design, analytics, community engagement strategies, and research training.

The microenvironmental modelling approach to assess children's exposure to air pollution - A review

Exposures to a wide spectrum of air pollutants were associated to several effects on children's health. Exposure assessment can be used to establish where and how air pollutants' exposures occur. However, a realistic estimation of children's exposures to air pollution is usually a great ethics challenge, especially for young children, because they cannot intentionally be exposed to contaminants and according to Helsinki declaration, they are not old enough to make a decision on their participation. Additionally, using adult surrogates introduces bias, since time-space-activity patterns are different from those of children. From all the different available approaches for exposure assessment, the microenvironmental (ME) modelling (indirect approach, where personal exposures are estimated or predicted from microenvironment measurements combined with time-activity data) seemed to be the best to assess children's exposure to air pollution as it takes into account the varying levels of pollution to which an individual is exposed during the course of the day, it is faster and less expensive. Thus, this review aimed to explore the use of the ME modelling approach methodology to assess children's exposure to air pollution. To meet this goal, a total of 152 articles, published since 2002, were identified and titles and abstracts were scanned for relevance. After exclusions, 26 articles were fully reviewed and main characteristics were detailed, namely: (i) study design and outcomes, including location, study population, calendar time, pollutants analysed and purpose; and (ii) data collection, including time-activity patterns (methods of collection, record time and key elements) and pollution measurements (microenvironments, methods of collection and duration and time resolution). The reviewed studies were from different parts of the world, confirming the worldwide application, and mostly cross-sectional. Longitudinal studies were also found enhancing the applicability of this approach. The application of this methodology on children is different from that on adults because of data collection, namely the methods used for collecting time-activity patterns must be different and the time-activity patterns are itself different, which leads to select different microenvironments to the data collection of pollutants' concentrations. The most used methods to gather information on time-activity patterns were questionnaires and diaries, and the main microenvironments considered were home and school (indoors and outdoors). Although the ME modelling approach in studies to assess children's exposure to air pollution is highly encouraged, a validation process is needed, due to the uncertainties associated with the application of this approach.

Sequential discriminant classification of environments with different levels of exposure to tobacco smoke

The use of biomarkers permits the detection of smoking having taken place in an environment. However, no single biomarker is able to differentiate clearly between different types of environments. Multivariate classification models have helped us to differentiate between outdoors, non-smoking indoors, well ventilated smoking indoors, and smoking environments without good air exchange. We found that the variables that enabled us to classify environments most accurately were indoor temperature, 2,5-dimethylfuran and ethyltoluene. A successful prediction rate of 86.5% was obtained by applying both direct fitting and cross validation discriminant (leave-one-out) analyses. Our results show that although a good air exchange ratio decreases the levels of volatile organic compounds in indoor air due to tobacco smoke, significant contamination still remains.

Modelling of human exposure to air pollution in the urban environment: a GPS-based approach

The main objective of this work was the development of a new modelling tool for quantification of human exposure to traffic-related air pollution within distinct microenvironments by using a novel approach for trajectory analysis of the individuals. For this purpose, mobile phones with Global Positioning System technology have been used to collect daily trajectories of the individuals with higher temporal resolution and a trajectory data mining, and geo-spatial analysis algorithm was developed and implemented within a Geographical Information System to obtain time-activity patterns. These data were combined with air pollutant concentrations estimated for several microenvironments. In addition to outdoor, pollutant concentrations in distinct indoor microenvironments are characterised using a probabilistic approach. An example of the application for PM2.5 is presented and discussed. The results obtained for daily average individual exposure correspond to a mean value of 10.6 and 6.0-16.4 μg m(-3) in terms of 5th-95th percentiles. Analysis of the results shows that the use of point air quality measurements for exposure assessment will not explain the intra- and inter-variability of individuals' exposure levels. The methodology developed and implemented in this work provides time-sequence of the exposure events thus making possible association of the exposure with the individual activities and delivers main statistics on individual's air pollution exposure with high spatio-temporal resolution.

What are the manifestations of ocular exposure to epichlorohydrin?

The Occupational Medicine Forum is prepared by the ACOEM Occupational and Environmental Medical Practice Committee and does not necessarily represent an official ACOEM position. The Forum is intended for health professionals and is not intended to provide medical or legal advice, including illness prevention, diagnosis or treatment, or regulatory compliance. Such advice should be obtained directly from a physician and/or attorney.

A discussion of exposure science in the 21st century: a vision and a strategy

BACKGROUND

The National Research Council (NRC) of the National Academy of Sciences recently published the report Exposure Science in the 21st Century: A Vision and a Strategy. The expert committee undertaking this report included expertise from ecology, chemistry, exposure science, toxicology, public health, bioethics, engineering, medicine, and policy.

OBJECTIVE

Our aim is to inform members of the scientific community in fields aligned with environmental and public health so they are more able to appreciate the full breadth of the vision and understand the framework developed in order to move the vision forward.

DISCUSSION

Although the NRC report was commissioned by the U.S. Environmental Protection Agency and the National Institute of Environmental Health Sciences, it is solely the consensus product of the independent volunteer committee, whose findings were subject to the rigorous peer-review procedures of the NRC. In addition to reviewing the history and current status of exposure science, the report lays out a vision for the future and makes recommendations that include both short-term and long-term milestones.

CONCLUSION

To accomplish the vision presented in the NRC report, resources will be needed to complete studies, develop and use analyses of exposure, and build databases associated with individual and population exposures, as well as to train the next generation of exposure scientists. Important excerpts as well as paraphrased statements from the report appear in this commentary; however, the general observations and comments are our own.

Two decades of exposure assessment studies on chromate production waste in Jersey City, New Jersey--what we have learned about exposure characterization and its value to public health and remediation

During much of the twentieth century, Jersey City, New Jersey was the leading center of chromate production in the United States. Chromate production produced huge volumes of chromium ore-processing residue containing many parts per million of hexavalent chromium. Starting in the 1990s, we undertook a series of studies to identify exposed populations, sources and pathways of exposure and the effectiveness of remediation activities in Jersey City. These studies revealed the effectiveness and success of the remediation activities. The sequence of studies presented here, builds on the lessons learned from each preceding study and illustrates how these studies advanced the field of exposure science in important ways, including the use of household dust as a measure of exposure to contaminants originating in the outdoor environment; development of effective and reproducible dust sampling; use of household dust to track temporal changes in exposure; understanding of the spatial relationship between sources of passive outdoor particulate emissions and residential exposure; use of focused biomonitoring to assess exposure under conditions of large inter-individual variability; and utility of linking environmental monitoring and biomonitoring. For chromium, the studies have demonstrated the use of Cr(+6)-specific analytical methods for measuring low concentrations of Cr(+6) in household dust and understanding of the occurrence of Cr(+6) in the background residential environment. We strongly recommend that environmental and public health agencies evaluate sites for their potential for off-site exposure and apply these tools in cases with significant potential as appropriate. This approach is especially important when contamination is widespread and/or a large population is potentially exposed. In such cases, these tools should be used to identify, characterize and then reduce the exposure to the off-site as well as on-site population. Importantly, these tools can be used in a demonstrable and quantifiable manner to provide both clarity and closure to concerned stakeholders.

The evolution of EPA's Exposure Factors Handbook and its future as an exposure assessment resource

The need to compile and summarize exposure factors data into a resource document was first established in 1983 after the publication of the National Academy of Sciences (NAS) report on Risk Assessment in the Federal Government: Managing the Process and subsequent publication of the Environmental Protection Agency's (EPA's) exposure guidelines in 1986 (NAS, 1983; US EPA, 1986). During the same time frame, the EPA published a report entitled Development of Statistical Distributions or Ranges of Standard Factors Used in Exposure Assessment to promote consistency among various exposure assessment activities in which EPA was involved and to serve as a support document to the 1986 exposure guidelines (US EPA, 1985). As the exposure assessment field continued to advance during the 1980s and 1990s, so did the need for more comprehensive data on exposure factors. The Exposure Factors Handbook was first published in 1989 in response to this need (US EPA, 1989). It became an important reference document and has been revised and updated since its original publication (US EPA, 1989; US EPA, 1997a; US EPA, 2011a). This paper reviews the evolution of the Exposure Factors Handbook, and explores anticipated needs and some of the potential options for future updates of the handbook.

Evaluation of organochlorine pesticides in breast milk samples in Turkey applying features of the partial order technique

Exposure data to organochlorine pesticides (OCPs) of mothers' breast milk samples were measured in different locations in the Taurus Mountains/Turkey. Villages at five altitudes were looked upon. The data analysis method applied is the Hasse diagram technique, based on Discrete Mathematics. For each of the five regions, one Hasse diagram was calculated and showed the same maximal object, namely, p-p'-Dichlorodiphenyldichloroethane (DDE). In a further data investigation step, we performed the similarity analyses of the locations in order to quantify the similarities and incomparabilities. It was revealed that no correlation exists between most altitudes and the pattern of contamination of breast milk samples. The two lowest situated areas, Sahil at sea level and Ciftlikköy at 121 m above sea level were similar. We reduced the datasets by applying the interval analysis followed by similarity analyses. We observed that endrin (END1), mirex (MIRE), and pentachlorobenzene (PECB) reduce most severely the similarity.

New approach for particulate exposure monitoring: determination of inhaled particulate mass by 24 h real-time personal exposure monitoring

The objectives of this study were to measure particulate pollution (PM(10), PM(2.5), and PM(1.0)) continuously (24 h/day for 7 day) using real-time exposure monitoring and to estimate total inhalation mass using breathing rate and time-activity. Breathing rates were calculated from measured heart rates. Participants were asked to record a time-activity diary every 15 min. Five microenvironments were defined based on the time-activity diary: home, workplace/school, other indoor, outdoor, and transportation. The average masses of inhaled PM(10) were 530, 316, and 280 μg/day for two office workers, a housewife, and three students, respectively; those of PM(2.5) were 316, 279, and 210 μg/day; and those of PM(1.0) were 251, 264, and 187 μg/day, respectively. We found that home and office/school microenvironments were the main contributors of PM(10), PM(2.5), and PM(1.0) inhaled mass during weekdays and weekends because dwelling time was a determinant factor for inhaled mass. Considering microenvironmental concentration, breathing rate, and dwelling time in each microenvironment, indoor home microenvironments were the largest source of particulate inhalation, followed in order by workplace, transportation, other indoor, and outdoor microenvironments. 34.6% and 69.6% of PM(10) inhalation mass were accumulated in home microenvironments during weekdays and weekends, respectively. The inhaled mass of particulate <1.0 μm (PM(1.0)) in size occupied largest, followed in order by particulate 10-2.5 μm (coarse particle) and 2.5-1.0 μm in size for all occupations.

Potential for inhalation exposure to engineered nanoparticles from nanotechnology-based cosmetic powders

BACKGROUND

The market of nanotechnology-based consumer products is rapidly expanding, and the lack of scientific evidence describing the accompanying exposure and health risks stalls the discussion regarding its guidance and regulation.

OBJECTIVES

We investigated the potential for human contact and inhalation exposure to nanomaterials when using nanotechnology-based cosmetic powders and compare them with analogous products not marketed as nanotechnology based.

METHODS

We characterized the products using transmission electron microscopy (TEM) and laser diffraction spectroscopy and found nanoparticles in five of six tested products. TEM photomicrographs showed highly agglomerated states of nanoparticles in the products. We realistically simulated the use of cosmetic powders by applying them to the face of a human mannequin head while simultaneously sampling the released airborne particles through the ports installed in the mannequin's nostrils.

RESULTS

We found that a user would be exposed to nanomaterial predominantly through nanoparticle-containing agglomerates larger than the 1-100-nm aerosol fraction.

CONCLUSIONS

Predominant deposition of nanomaterial(s) will occur in the tracheobronchial and head airways--not in the alveolar region as would be expected based on the size of primary nanoparticles. This could potentially lead to different health effects than expected based on the current understanding of nanoparticle behavior and toxicology studies for the alveolar region.

Providing the missing link: the exposure science ontology ExO

Environmental health information resources lack exposure data required to translate molecular insights, elucidate environmental contributions to diseases, and assess human health and ecological risks. We report development of an Exposure Ontology, ExO, designed to address this information gap by facilitating centralization and integration of exposure data. Major concepts were defined and the ontology drafted and evaluated by a working group of exposure scientists and other ontology and database experts. The resulting major concepts forming the basis for the ontology are "exposure stressor", "exposure receptor", "exposure event", and "exposure outcome". Although design of the first version of ExO focused on human exposure to chemicals, we anticipate expansion by the scientific community to address exposures of human and ecological receptors to the full suite of environmental stressors. Like other widely used ontologies, ExO is intended to link exposure science and diverse environmental health disciplines including toxicology, epidemiology, disease surveillance, and epigenetics.

Exposure science for terrorist attacks and theaters of military conflict: minimizing contact with toxicants

The strategies for protecting our deployed U.S. Forces are outlined in National Research Council documents published in 1999-2000. This article summarizes experiences and information gathered and interpreted regarding population and rescue workers' exposures in the aftermath of the 2001 World Trade Center attacks, with the aim to provide insights on issues related to military deployment to locations with hazardous agents. Issues covered include phases of exposure, materials of concern, detection equipment, and personal protection equipment. The focus is on human exposure issues, which are primarily associated with strategies 1 through 3 of the National Research Council's report entitled "Protecting Those Who Serve: Strategies to Protect the Health of Deployed U.S. Forces". Contact and duration of contact with hazardous substances are critical areas of concern, which require prevention and intervention procedures and protocols to reduce the incidence of acute and long-term health outcomes.

New Jersey: a case study of the reduction in urban and suburban air pollution from the 1950s to 2010

BACKGROUND

Air pollution has been a topic of intense concern and study for hundreds of years. During the second half of the 20th century, the United States implemented regulations and controls to reduce the levels of criteria air pollutants and achieve the National Ambient Air Quality Standards (NAAQS) for the protection of human health, while concurrently reducing the levels of toxic air pollutants.

OBJECTIVE

In this commentary we trace the changes in air pollution in New Jersey as a case study, demonstrating the impact of local, state, and federal strategies to control emissions of pollutants and pollutant precursors from the 1950s until today.

DISCUSSION

The original NAAQS (1970-1995) have been achieved, and significant progress has been made to achieve revised standards for ozone and particulate matter (PM) < 2.5 µm in aerodynamic diameter (PM2.5) in New Jersey, which in the past was considered a highly polluted industrial state.

CONCLUSIONS

Assuming no reversals on current regulations because of some major event or energy infrastructure disruption, outdoor air pollution reductions will continue to address health risks among specific segments of the general population affected by ozone/PM and pollution caused by neighborhood, local, and regional point and mobile sources.

Potential for exposure to engineered nanoparticles from nanotechnology-based consumer spray products

The potential for human exposure to engineered nanoparticles due to the use of nanotechnology-based consumer sprays (categorized as such by the Nanotechnology Consumer Products Inventory) is examined along with analogous products, which are not specified as nanotechnology-based (regular products). Photon correlation spectroscopy was used to obtain particle size distributions in the initial liquid products. Transmission electron microscopy was used to determine particle size, shape, and agglomeration of the particles. Realistic application of the spray products near the human breathing zone characterized airborne particles that are released during use of the sprays. Aerosolization of sprays with standard nebulizers was used to determine their potential for inhalation exposure. Electron microscopy detected the presence of nanoparticles in some nanotechnology-based sprays as well as in several regular products, whereas the photon correlation spectroscopy indicated the presence of particles <100 nm in all investigated products. During the use of most nanotechnology-based and regular sprays, particles ranging from 13 nm to 20 μm were released, indicating that they could he inhaled and consequently deposited in all regions of the respiratory system. The results indicate that exposures to nanoparticles as well as micrometer-sized particles can be encountered owing to the use of nanotechnology-based sprays as well as regular spray products.