207c - Advancement of exposure science and its application in occupational hygiene

Workshop report

BackgroundHuman exposure to micro- and nanoplastic particles (MNPs) is inevitable but human health risk assessment remains challenging for several reasons. MNPs are complex mixtures of particles derived from different polymer types, which may contain plenty of additives and/or contaminants. MNPs cover broad size distributions and often have irregular shapes and morphologies. Moreover, several of their properties change over time due to aging/ weathering. Case-by-case assessment of each MNP type does not seem feasible, more straightforward methodologies are needed. However, conceptual approaches for human health risk assessment are rare, reliable methods for exposure and hazard assessment are largely missing, and meaningful data is scarce.MethodsHere we reviewed the state-of-the-art concerning risk assessment of chemicals with a specific focus on polymers as well as on (nano-)particles and fibres. For this purpose, we broadly screened relevant knowledge including guidance documents, standards, scientific publications, publicly available reports. We identified several suitable concepts such as: (i) polymers of low concern (PLC), (ii) poorly soluble low toxicity particles (PSLT) and (iii) fibre pathogenicity paradigm (FPP). We also aimed to identify promising methods, which may serve as a reasonable starting point for a test strategy.Results and conclusionHere, we propose a state-of-the-art modular risk assessment framework for MNPs, focusing primarily on inhalation as a key exposure route for humans that combines several integrated approaches to testing and assessment (IATAs). The framework starts with basic physicochemical characterisation (step 1), followed by assessing the potential for inhalative exposure (step 2) and includes several modules for toxicological assessment (step 3). We provide guidance on how to apply the framework and suggest suitable methods for characterization of physicochemical properties, exposure and hazard assessment. We put special emphasis on new approach methodologies (NAMs) and included grouping, where adequate. The framework has been improved in several iterative cycles by taking into account expert feedback and is currently being tested in several case studies. Overall, it can be regarded as an important step forward to tackle human health risk assessment.

In the risk assessment of chemical substances, aggregation of exposure to a substance from different sources via different pathways is not common practice. Focusing the exposure assessment on a substance from a single source can lead to a significant underestimation of the risk. To gain more insight on how to perform an aggregate exposure assessment, we applied a deterministic (tier 1) and a person-oriented probabilistic approach (tier 2) for exposure to the four most common parabens through personal care products in children between 0 and 3 years old. Following a deterministic approach, a worst-case exposure estimate is calculated for methyl-, ethyl-, propyl- and butylparaben. As an illustration for risk assessment, Margins of Exposure (MoE) are calculated. These are 991 and 4966 for methyl- and ethylparaben, and 8 and 10 for propyl- and butylparaben, respectively. In tier 2, more detailed information on product use has been obtained from a small survey on product use of consumers. A probabilistic exposure assessment is performed to estimate the variability and uncertainty of exposure in a population. Results show that the internal exposure for each paraben is below the level determined in tier 1. However, for propyl- and butylparaben, the percentile of the population with an exposure probability above the assumed “safe” MoE of 100, is 13% and 7%, respectively. In conclusion, a tier 1 approach can be performed using simple equations and default point estimates, and serves as a starting point for exposure and risk assessment. If refinement is warranted, the more data demanding person-oriented probabilistic approach should be used. This probabilistic approach results in a more realistic exposure estimate, including the uncertainty, and allows determining the main drivers of exposure. Furthermore, it allows to estimate the percentage of the population for which the exposure is likely to be above a specific value.

“AMORE” Decision Support System for probabilistic Ecological Risk Assessment - Part I: Exposure and risk assessment of the case study on cyanide

Poor air quality is a leading contributor to the global disease burden and total number of deaths worldwide. Humans spend most of their time in built environments where the majority of the inhalation exposure occurs. Indoor Air Quality (IAQ) is challenged by outdoor air pollution entering indoors through ventilation and infiltration and by indoor emission sources. The aim of this study was to understand the current knowledge level and gaps regarding effective approaches to improve IAQ. Emission regulations currently focus on outdoor emissions, whereas quantitative understanding of emissions from indoor sources is generally lacking. Therefore, specific indoor sources need to be identified, characterized, and quantified according to their environmental and human health impact. The emission sources should be stored in terms of relevant metrics and statistics in an easily accessible format that is applicable for source specific exposure assessment by using mathematical mass balance modelings. This forms a foundation for comprehensive risk assessment and efficient interventions. For such a general exposure assessment model we need 1) systematic methods for indoor aerosol emission source assessment, 2) source emission documentation in terms of relevant a) aerosol metrics and b) biological metrics, 3) default model parameterization for predictive exposure modeling, 4) other needs related to aerosol characterization techniques and modeling methods. Such a general exposure assessment model can be applicable for private, public, and occupational indoor exposure assessment, making it a valuable tool for public health professionals, product safety designers, industrial hygienists, building scientists, and environmental consultants working in the field of IAQ and health.

Objectives: Exposure Assessment for workplace hazards where the exposure level is below occupational exposure limits(OELs) has been performed without considering either the degrees of risk or exposure levels and has failed to lead to intervention in many cases. The objective of this study was to suggest and test an application framework for risk assessment methodology under the current exposure assessment system in Korea. Materials: First, we investigated the exposure assessment systems in Korea and other countries. To adopt some risk assessment techniques, we also analyzed risk assessment systems and compared them to exposure assessment systems. A few suggestions were made. We held a public hearing during an industrial hygiene conference and took surveys using a questionnaire. Results: The first suggestion was to implement the risk assessment and exposure assessment through a "one-stop" system. In that case, one expected question would be who has been doing the jobs so far. In most cases, industrial hygiene consulting services or laboratories have been performing exposure assessment for business owners. Business owners are required to perform risk assessment. As two different groups of people will be required to implement two things in a one-stop system, they need to share information. As an information vehicle to share information, commonly filed survey checklists were suggested. The second suggestion was to categorize exposure level into four groups instead of the current binary divisions based on OELs. In the risk assessment system, exposure level is divided into four groups utilizing the cut-points of 10%, 50%, and 100% of OELs. The same schema can be adopted in the exposure assessment system and different levels of requirements can be assigned for each group. The third suggestion was regarding the regulation system. To provide the suggestions some thrust toward being implemented in the field, changes should be made in the legal system. Two different types of new exposure assessment result reporting forms were suggested. Some investigations such as an ergonomic survey are officially accepted as risk assessment under the current legal system. A few items were suggested to be included in the exposure assessment result reporting to be accepted as risk assessment. A pilot study in two small factories was performed and pointed out the strengths and weakness of our suggestions. Conclusions: Discussions and studies on the improvement of the exposure assessment system have been held for decades and no tangible changes have yet been made. We hope this result can help realize healthy lives for workers in Korea.

Embraced as a breaking through methodological framework, the exposome is accompanied by novel exposure assessment methods and data processing tools or models. However, systematic mapping of the landscape of exposome studies, including their characteristics, components, tools and language has not been done so far. We conducted a scoping review to answer the question: “Which main domains of the human exposome have been included in the literature and which metrics of exposure(s)/outcome(s) have been used?” We performed a comprehensive search of human studies containing the word “exposom*” and published up to March 8, 2019. We screened 1133 records and 82 studies were included in the analysis. Most studies took place in Europe. Data analysis showed the non-systematic use of the exposome term. Most studies had a longitudinal design (n = 30, 37%), were conducted on adults (n = 40, 51%), and had a clearly defined health outcome in methodology (n = 48, 61%). Omics tools, such as metabolomics were used in 38 studies (49%), while environment-wide association analysis was used in 9 studies (11%). Thirty-seven (48%) studies included all three exposome domains (general external, specific external and internal) while 33 (42%) studies included two. Despite the large number of environmental components that comprise each of the exposome domains, only a subset has been currently studied. An optimized consideration of the components from all exposome domains, as well as the standardization of the exposure and outcome assessment methods is warranted to advance the utility of the human exposome concept.

Work-Relatedness.

The EU‐FORA Fellowship Programme ‘Integration of tools and social science into food safety risk assessments’ was proposed by the Food Standards Agency (FSA), the government department responsible for food safety in the UK. The working programme was organised into four modules, covering different areas of risk assessment, including microbiological risk assessment, chemical risk assessment, exposure assessment, risk prioritisation and the integration of risk assessment with social science. During this period, the fellow had the unique opportunity to gain experience in different fields of risk assessment, namely how to conduct a systematic review, to assess the risk of microbiological and chemical hazards, to make use of modelling tools for exposure assessment and risk prioritisation, to write scientific reports for committees and networks at the national level and to understand the role of social science in risk assessment. In addition, the fellow was able to attend several meetings, seminars, courses and workshops that helped him to gain further insight in the field of food science. The complete programme enabled a fast learning curve that allowed the fellow to have an overview of the different tools that can be employed in the wide field of food safety risk assessment, in order to acquire skills and competences that can be used in his future career.

Envisioning an international validation process for New Approach Methodologies in chemical hazard and risk assessment

Background and Aims: Potential risk to health from waste disposal in landfills is a public concern issue and this concern is based on equivocal evidence. The main conclusion of the overall assessment of the literature about waste management and health is that adverse effects evidence for population living near landfill is usually insufficient and inconclusive. A major problem is the weakness of quantitative exposure information and exposure assessment methods. We propose here exposure assessment based on a multi-disciplinary approach where emissions and ambient samples are characterized to assess exposure to potential hazards. Methods: A multi year follow-up has been undertaken for two landfills that accepts non-hazardous solid waste. Exposure assessment was based on measured emissions from the landfill, both from landfill gas energy recovery systems and from uncontrolled surface emissions. Emissions and atmospheric concentrations have been assessed with analytical campaigns, sampling the main known carcinogenic compounds emitted from landfills coming both from landfill gas torch combustion (dioxins, furanes and PAHs) and from diffusive emissions (VCM and benzene). Exposure assessments were based on receptor’s concentrations, using atmospheric dispersion models to estimate maximum concentrations and depositions in correspondence to sensitive receptors. Results: Emissions from two different plants have been measured both for non-methanic volatile organic compounds PAHs and dioxin-like compounds. Results from diffusion modelling indicated limited exposure for identified receptors, with differences from year to year. Risk assessment has been performed both for carcinogenic and non carcinogenic assessment, showing acceptable risk. Conclusion: Direct exposure measurements play a key role in order to improve the epidemiological studies for populations living in areas where waste management facilities are located or planned. A standardized approach, that might be discussed starting from this example, could become, within few years, a new instrument for environmental epidemiology in this complex problem, at least until reliable biomarkers will be available.

This paper describes a battery of physical exposure assessment methods used in a large prospective upper extremity musculoskeletal disorders study. Different from some previous prospective studies, this study collects health and physical exposure data for each study subject rather than at a group level. Subjects are recruited from different job categories based on their hand activity exposure categories. Multiple exposure assessment methods are used to measure job physical exposures such as force, repetition, and work posture. This will allow us to compare the sensitivity of different exposure assessment methods in predicting the risk for upper extremity musculoskeletal disorders. Procedures have also been taken to monitor inter-observer reliability for some observational analyses. During the first year of the study, baseline exposure measurements have been collected from 607 volunteers at 11 different worksites. Follow-up measurements have also been collected in these worksites. Whenever a participant has a significant job change, a new exposure assessment is conducted at the new job. This paper will primarily discuss the various exposure assessment methods used in this study, and use some preliminary results to demonstrate some of the data reduction methods.

The PRIMATE study is an Italian translational research project, which aims to identify personalized biomarkers associated with clinical characteristics of malignant pleural mesothelioma (MPM). For this purpose, characteristics of MPM patients with different degrees of asbestos exposure will be compared to identify somatic mutations, germline polymorphism, and blood inflammatory biomarkers. In this framework, we assessed exposure to asbestos for 562 cases of MPM extracted from the Lombardy region Mesothelioma Registry (RML), for which a complete interview based on a standardized national questionnaire and histopathological specimens were available. Exposure assessment was performed: (1) through experts' evaluation (considered as the gold standard for the purpose of this study), according to the guidelines of the Italian National Mesothelioma Registry (ReNaM) and (2) using a job-exposure matrix (SYN-JEM) to obtain qualitative (ever/never) and quantitative estimates of occupational asbestos exposure (cumulative exposure expressed in fibers per mL (f/mL)). The performance of SYN-JEM was evaluated against the experts' evaluation. According to experts' evaluation, occupational asbestos exposure was recognized in 73.6% of men and 23.6% of women; furthermore, 29 men (7.8%) and 70 women (36.9%) had non-occupational exposure to asbestos. When applying SYN-JEM, 225 men (60.5%) and 25 women (13.2%) were classified as occupationally exposed, with a median cumulative exposure higher for men (1.7 f/mL-years) than for women (1.2 f/mL-years). The concordance between the two methods (Cohen’s kappa) for occupational exposure assessment was 0.46 overall (0.41 in men, and 0.07 in women). Sensitivity was higher in men (0.73) than in women (0.18), while specificity was higher in women (0.88) than in men (0.74). Overall, both methods can be used to reconstruct past occupational exposure to asbestos, each with its own advantages and limitations.

Background:High quality personal exposure data is fundamental to understanding the health implications of household energy interventions, interpreting analyses across assigned study arms, and characterizing exposure–response relationships for household air pollution. This paper describes the exposure data collection for the Household Air Pollution Intervention Network (HAPIN), a multicountry randomized controlled trial of liquefied petroleum gas stoves and fuel among 3,200 households in India, Rwanda, Guatemala, and Peru.Objectives:The primary objectives of the exposure assessment are to estimate the exposure contrast achieved following a clean fuel intervention and to provide data for analyses of exposure–response relationships across a range of personal exposures.Methods:Exposure measurements are being conducted over the 3-y time frame of the field study. We are measuring fine particulate matter [PM in aerodynamic diameter ()] with the Enhanced Children’s MicroPEM™ (RTI International), carbon monoxide (CO) with the USB-EL-CO (Lascar Electronics), and black carbon with the OT21 transmissometer (Magee Scientific) in pregnant women, adult women, and children of age, primarily via multiple 24-h personal assessments (three, six, and three measurements, respectively) over the course of the 18-month follow-up period using lightweight monitors. For children we are using an indirect measurement approach, combining data from area monitors and locator devices worn by the child. For a subsample (up to 10%) of the study population, we are doubling the frequency of measurements in order to estimate the accuracy of subject-specific typical exposure estimates. In addition, we are conducting ambient air monitoring to help characterize potential contributions of exposure from background concentration. Stove use monitors (Geocene) are being used to assess compliance with the intervention, given that stove stacking (use of traditional stoves in addition to the intervention gas stove) may occur.Conclusions:The tools and approaches being used for HAPIN to estimate personal exposures build on previous efforts and take advantage of new technologies. In addition to providing key personal exposure data for this study, we hope the application and learnings from our exposure assessment will help inform future efforts to characterize exposure to household air pollution and for other contexts. https://doi.org/10.1289/EHP6422

A survey was undertaken among Swiss occupational hygienists and other professionals to identify the different exposure assessment methods used, the contextual parameters observed and the uses, difficulties and possible developments of exposure models for field application. A questionnaire was mailed to 121 occupational hygienists, all members of the Swiss Occupational Hygiene Society. A shorter questionnaire was also sent to registered occupational physicians and selected safety specialists. Descriptive statistics and multivariate analyses were performed. The response rate for occupational hygienists was 60%. The so-called expert judgement appeared to be the most widely used method, but its efficiency and reliability were both judged with very low scores. Long-term sampling was perceived as the most efficient and reliable method. Various determinants of exposure, such as emission rate and work activity, were often considered important, even though they were not included in the exposure assessment processes. Near field local phenomena determinants were also judged important for operator exposure estimation. Exposure models should be improved to integrate factors which are more easily accessible to practitioners. Descriptors of emission and local phenomena should also be included.