Methods to assess dermal exposures in occupational settings: a scoping review.

OBJECTIVES: The dermal exposure route is expected to become increasingly significant relative to total worker exposure as inhalational exposure limits continue to decrease. However, standardization of occupational exposure assessment methods and scientific consensus are needed. This is the first scoping review mapping the literature across all dermal exposure assessment methods and their targeted substances/chemicals in occupational settings. METHODS: Eligibility criteria broadly included studies reporting any noninvasive dermal exposure assessment method in an occupational setting. The literature search (Web of Science and MEDLINE) was restricted to peer-reviewed, primary literature published in the last 20 years (2002-2022). Titles/abstracts were dual independently screened. Data charting was performed by a single reviewer using standard template. All stages were pilot tested. The JBI (formerly, the Joanna Briggs Institute) scoping review methods and PRISMA-ScR checklist (Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews) were used. RESULTS: In total, 493 articles were data charted and categorized by 4 study types: methods development (22%), exposure assessment (51%), health outcomes (21%), and controls assessment (6%). Fourteen types of dermal exposure assessment methods were charted with biomarkers (51%), dosimeters (21%), and qualitative assessments such as questionnaires or surveys (17%) most common. Seventeen different chemicals/substances were charted; pesticides (28%) and polycyclic aromatic hydrocarbons (PAHs) (22%) associated with crude oil products and combustion were most common. Mapping between substances and exposure assessment method categories, pesticide dosimeters (11%), and PAH biomarker studies (14%) were most reported. Literature gaps were identified for cleaning agents, hair dyes, glycol ether, N,N-dimethylformamide/N-methyl-2-pyrrolidone, dioxins, and bisphenol A. CONCLUSIONS: To foster scientific consensus, standardization across study reporting is needed for describing: (i) exposure assessment methods used, (ii) worker tasking/conditions, (iii) targeted substances and substance state, and (iv) targeted exposure routes. Overall, this review categorizes, maps, and defines the scope of literature for occupational dermal exposure assessment methods.

Estimating exposures from spray products using robotic simulations.

There is an increasing need for exposure data to enable more precise information for risk estimates and improved public health protection. While personal monitoring data are preferred, it is often difficult to collect due to the resources needed to complete a human research study. In this study, we successfully programmed a robotic arm to mimic human use (spraying) of a fabric crafts protector (FCP) and human cleaning (spraying and wiping) of a glass pane with glass cleaner (GC). The robot was then used in place of human subjects to assess inhalation exposures to volatile organic compounds (VOCs) during the use of the FCP and GC. Air sampling data were collected while the robot used the products to estimate personal exposures to VOCs. Average VOC concentrations were 1.57 ppm for FCP spraying and 0.17 ppm for GC spraying and wiping. During FCP spraying, average acetone concentrations were 0.88 ppm and average isopropyl alcohol concentrations were 0.26 ppm. During GC spraying and wiping, average 2-butoxyethanol concentrations were 0.15 ppm. Air sampling data were found to be within the range of data reported in the literature during human use of similar glass cleaning products. No data was found in the literature during use of fabric protector spray products. This study contributes exposure measurement data with detailed contextual information to help characterize inhalation exposures during the use of 2 spray products. In addition, the study offers a systematic, efficient method for generating exposure data which can be used to improve health and safety risk assessments used for public health protection.

Fine organic particulate matter dominates indoor-generated PM2.5 in RIOPA homes.

Residential indoor and outdoor fine particle (PM(2.5)) organic (OC) and elemental carbon (EC) concentrations (48 h) were measured at 173 homes in Houston, TX, Los Angeles County, CA, and Elizabeth, NJ as part of the Relationship of Indoor, Outdoor and Personal Air (RIOPA) study. The adsorption of organic vapors on the quartz fiber sampling filter (a positive artifact) was substantial indoors and out, accounting for 36% and 37% of measured OC at the median indoor (8.2 microg C/m(3)) and outdoor (5.0 microg C/m(3)) OC concentrations, respectively. Uncorrected, adsorption artifacts would lead to substantial overestimation of particulate OC both indoors and outdoors. After artifact correction, the mean particulate organic matter (OM=1.4 OC) concentration indoors (9.8 microg/m(3)) was twice the mean outdoor concentration (4.9 microg/m(3)). The mean EC concentration was 1.1 microg/m(3) both indoors and outdoors. OM accounted for 29%, 30% and 29% of PM(2.5) mass outdoors and 48%, 55% and 61% of indoor PM(2.5) mass in Los Angeles Co., Elizabeth and Houston study homes, respectively. Indirect evidence provided by species mass balance results suggests that PM(2.5) nitrate (not measured) was largely lost during outdoor-to-indoor transport, as reported by Lunden et al. This results in dramatic changes with outdoor-to-indoor transport in the mass and composition of ambient-generated PM(2.5) at California homes. On average, 71% to 76% of indoor OM was emitted or formed indoors, calculated by (1) Random Component Superposition (RCS) model and (2) non-linear fit of OC and air exchange rate data to the mass balance model. Assuming that all particles penetrate indoors (P=1) and there is no particle loss indoors (k=0), a lower bound estimate of 41% of indoor OM was indoor-generated (mean). OM appears to be the predominant species in indoor-generated PM(2.5), based on species mass balance results. Particulate OM emitted or formed indoors is substantial enough to alter the concentration, composition and behavior of indoor PM(2.5). One interesting effect of increased indoor OM concentrations is a shift in the gas-particle partitioning of polycyclic aromatic hydrocarbons (PAHs) from the gas to the particle phase with outdoor-to-indoor transport.

A meta-analytic approach for characterizing the within-worker and between-worker sources of variation in occupational exposure.

While many studies have quantified the sources of variation in exposure to workplace contaminants for individual groups of workers, patterns of exposure variability have not been investigated since a comprehensive evaluation was carried out over 10 years ago. Therefore, a systematic review of the literature was conducted to identify studies that applied the one-way random-effects model to describe exposure profiles of groups of workers classified on the basis of the kind of work performed and where it was performed. Quantitative estimates of the sources of variation in exposure along with information related to the workplace, contaminant and sampling strategy were compiled. For subsets of the data, based upon the classification scheme used to group workers, weighted empirical cumulative distribution functions were constructed and compared using the non-parametric Kolomogorov-Smirnov two-sample test. Further stratifications evaluated differences by industry, agent and characteristics of the sampling strategy. The review identified nearly 60 studies that examined the within-worker and between-worker sources of variation in exposure to workplace contaminants. In pooling results across studies, the between-worker variability increased as workers were aggregated across jobs and locations. The within-worker variability for an occupational group of workers was generally larger than the between-worker variability, although the differences in the variation in exposures across work shifts relative to the variation among workers' mean exposure levels diminished as groups were combined across jobs and locations. On average, gaseous exposures were more homogeneous than exposures to aerosols or dermal agents as were exposures in the chemical industry compared with the non-chemical industry. The design of sampling strategies also plays an important role with greater variability among groups of workers who were sampled randomly rather than systematically; in addition, differences were detected on the basis of the study period and sample size. In evaluating key features of the design and methods of the studies identified in the review, several methodological issues emerged given the heterogeneity in terms of how censored data were handled, which estimation method was applied and whether underlying assumptions of the models were met. Notwithstanding the utility of quantifying sources of variation in exposure, several challenges lie ahead with regard to ensuring quality in the collection, analysis and reporting of exposure monitoring data that would enhance efforts to accurately assess exposure.

Influence of ambient (outdoor) sources on residential indoor and personal PM2.5 concentrations: analyses of RIOPA data.

The Relationship of Indoor, Outdoor and Personal Air (RIOPA) study was designed to investigate residential indoor, outdoor and personal exposures to several classes of air pollutants, including volatile organic compounds, carbonyls and fine particles (PM2.5). Samples were collected from summer, 1999 to spring, 2001 in Houston (TX), Los Angeles (CA) and Elizabeth (NJ). Indoor, outdoor and personal PM2.5 samples were collected at 212 nonsmoking residences, 162 of which were sampled twice. Some homes were chosen due to close proximity to ambient sources of one or more target analytes, while others were farther from sources. Median indoor, outdoor and personal PM2.5 mass concentrations for these three sites were 14.4, 15.5 and 31.4 microg/m3, respectively. The contributions of ambient (outdoor) and nonambient sources to indoor and personal concentrations were quantified using a single compartment box model with measured air exchange rate and a random component superposition (RCS) statistical model. The median contribution of ambient sources to indoor PM2.5 concentrations using the mass balance approach was estimated to be 56% for all study homes (63%, 52% and 33% for California, New Jersey and Texas study homes, respectively). Reasonable variations in model assumptions alter median ambient contributions by less than 20%. The mean of the distribution of ambient contributions across study homes agreed well for the mass balance and RCS models, but the distribution was somewhat broader when calculated using the mass balance model with measured air exchange rates.

Relationship of Indoor, Outdoor and Personal Air (RIOPA) study: study design, methods and quality assurance/control results.

The Relationship of Indoor, Outdoor and Personal Air (RIOPA) Study was undertaken to evaluate the contribution of outdoor sources of air toxics, as defined in the 1990 Clean Air Act Amendments, to indoor concentrations and personal exposures. The concentrations of 18 volatile organic compounds (VOCs), 17 carbonyl compounds, and fine particulate matter mass (PM(2.5)) were measured using 48-h outdoor, indoor and personal air samples collected simultaneously. PM2.5 mass, as well as several component species (elemental carbon, organic carbon, polyaromatic hydrocarbons and elemental analysis) were also measured; only PM(2.5) mass is reported here. Questionnaires were administered to characterize homes, neighborhoods and personal activities that might affect exposures. The air exchange rate was also measured in each home. Homes in close proximity (<0.5 km) to sources of air toxics were preferentially (2:1) selected for sampling. Approximately 100 non-smoking households in each of Elizabeth, NJ, Houston, TX, and Los Angeles, CA were sampled (100, 105, and 105 respectively) with second visits performed at 84, 93, and 81 homes in each city, respectively. VOC samples were collected at all homes, carbonyls at 90% and PM(2.5) at 60% of the homes. Personal samples were collected from nonsmoking adults and a portion of children living in the target homes. This manuscript provides the RIOPA study design and quality control and assurance data. The results from the RIOPA study can potentially provide information on the influence of ambient sources on indoor air concentrations and exposure for many air toxics and will furnish an opportunity to evaluate exposure models for these compounds.

Air concentrations of VOCs in portable and traditional classrooms: results of a pilot study in Los Angeles County.

Recent state and federal public school class-size reduction initiatives, increased elementary and pre-K enrollment driven by population growth and immigration, and limited resources for capital projects, modernization, and maintenance at aging schools have increased the prevalence of prefabricated, portable classrooms (portables). At present, approximately one of three California students are taught in portables, whose use is especially prevalent in more populated counties such as Los Angeles, home to the nation's second largest school district. Limited data existed on chemical compound air concentrations, and thus exposures, inside American public schools. Measurements have been limited, usually performed in complaint schools, and varied in sampling protocols and analysis methods. To address a school environment and children's health issue of present concern, an assessment of public school portables was conducted in Los Angeles County. Seven schools in two school districts were recruited, from which 20 classrooms--13 portables, seven in main buildings--were randomly selected. We report indoor air concentrations of 21 target toxic and odorous volatile organic compounds (VOCs), including formaldehyde and acetaldehyde, measured with passive samplers (DNSH PAKS and 3M OVM 3500) in the cooling and heating seasons between June 2000 and June 2001. None of the measured indoor air formaldehyde concentrations exceeded the existing California Air Resources Board guideline (50 ppb, or 60 microg/m(3)). The main sources of aldehydes in classrooms, especially portables, were likely interior finish materials and furnishings made of particleboard without lamination. Indoor air VOC concentrations were generally low in this pilot study. The four most prevalent VOCs measured were toluene, m-/p-xylene, alpha-pinene, and delta-limonene; likely indoor sources were personal, teaching, and cleaning products. Future schools research should attempt larger samples over larger geographical areas.

Polycyclic aromatic hydrocarbons in the indoor and outdoor air of three cities in the U.S.

The indoor and outdoor concentrations of 30 polycyclic aromatic hydrocarbons (PAHs) were measured in 55 nonsmoking residences in three urban areas during June 1999-May 2000. The data represent the subset of samples collected within the Relationship of Indoor, Outdoor, and Personal Air study (RIOPA). The study collected samples from homes in Los Angeles, CA, Houston, TX, and Elizabeth, NJ. In the outdoor samples, the total PAH concentrations (sigmaPAH) were 4.2-64 ng m(-3) in Los Angeles, 10-160 ng m(-3) in Houston, and 12-110 ng m(-3) in Elizabeth. In the indoor samples, the concentrations of sigmaPAH were 16-220 ng m(-3) in Los Angeles, 21-310 ng m(-3) in Houston, and 22-350 ng m(-3) in Elizabeth. The PAH profiles of low molecular weight PAHs (3-4 rings) in the outdoor samples from the three cities were not significantly different. In contrast, the profiles of 5-7-ring PAHs in thesethree citieswere significantlydifferent, which suggested different dominant PAH sources. The signatures of 5-7-ring PAHs in the indoor samples in each city were similar to the outdoor profiles, which suggested that indoor concentrations of 5-7-ring PAHs were dominated by outdoor sources. Indoor-to-outdoor ratios of the PAH concentrations showed that indoor sources had a significant effect on indoor concentrations of 3-ring PAHs and a smaller effect on 4-ring PAHs and that outdoor sources dominated the indoor concentrations of 5-7-ring PAHs.