Application In Exposure Assessment Research Articles

Bioaccessibility characteristics of metals in welding fume and its application in exposure assessment

Objective: To explore the bioaccessibility of the main metal components in welding fume welding fume in simulated lung fluid, and to evaluate the exposure level of each metal component in combination with the EPA inhalation exposure risk assessment model. Methods: In November 2022, the microscopic morphology characteristics of welding fumes were analyzed by scanning electron microscopy, the bioaccessibility of each metal component in lung fluid simulated normal and lung inflammatory states was analyzed by in vitro simulation method, and the exposure level of each metal component was calculated in combination with the EPA inhalation exposure risk assessment model. Results: The main metal components in carbon dioxide gas shielded welding fumes were Fe, Mn, Zn, Ti, Al, Cu, Cr, Cd, Ni and As, and the bioaccessibility in simulated normal lung interstitial fluid was 0.82%-1.84%, 5.07%-9.41%, 4.52%-7.23%, 5.10%-8.67%, 20.48%-29.60%, 5.27%-9.83%, 4.80%-7.56%, 0.07%-1.08%, 6.48%-13.84% and 33.02%-42.81%. The bioaccessibility of the above metal components in the lung fluid under simulated lung inflammation was 14.79%-27.45%, 34.53%-46.11%, 35.31%-59.13%, 16.45%-22.51%, 60.78%-76.51%, 26.58%-34.12%, 15.32%-25.87%, 2.0%-5.7%, 34.77%-43.33% and 71.34%-88.36%, respectively. Compared with the simulated lurg interstitial fluid, the bioaccessibility of metal components in the lung fluid under the simulated inflammatory state was increased, and the difference was statistically significant (P<0.05). The average daily exposure dose Mn in the two simulated lung fluids exceeded the inhalation reference limit (>50 times), and the average daily exposure dose Ti and Cr in the simulated lung inflammation exceeded the reference limit (>1.3 times) . Conclusion: Attention should be paid to the bioaccessibility characteristics of metal components in the exposure level and hazard assessment of welding fumes.

Reducing the Influence of Environmental Factors on Performance of a Diffusion-Based Personal Exposure Kit.

Sensor technology has enabled the development of portable low-cost monitoring kits that might supplement many applications in conventional monitoring stations. Despite the sensitivity of electrochemical gas sensors to environmental change, they are increasingly important in monitoring polluted microenvironments. The performance of a compact diffusion-based Personal Exposure Kit (PEK) was assessed for real-time gaseous pollutant measurement (CO, O3, and NO2) under typical environmental conditions encountered in the subtropical city of Hong Kong. A dynamic baseline tracking method and a range of calibration protocols to address system performance were explored under practical scenarios to assess the performance of the PEK in reducing the impact of rapid changes in the ambient environment in personal exposure assessment applications. The results show that the accuracy and stability of the ppb level gas measurement is enhanced even in heterogeneous environments, thus avoiding the need for data post-processing with mathematical algorithms, such as multi-linear regression. This establishes the potential for use in personal exposure monitoring, which has been difficult in the past, and for reporting more accurate and reliable data in real-time to support personal exposure assessment and portable air quality monitoring applications.

Assessing viability and infectivity of foodborne and waterborne stages (cysts/oocysts) of Giardia duodenalis, Cryptosporidium spp., and Toxoplasma gondii: a review of methods.

Giardia duodenalis, Cryptosporidium spp. and Toxoplasma gondii are protozoan parasites that have been highlighted as emerging foodborne pathogens by the Food and Agriculture Organization of the United Nations and the World Health Organization. According to the European Food Safety Authority, 4786 foodborne and waterborne outbreaks were reported in Europe in 2016, of which 0.4% were attributed to parasites including Cryptosporidium, Giardia and Trichinella. Until 2016, no standardized methods were available to detect Giardia, Cryptosporidium and Toxoplasma (oo)cysts in food. Therefore, no regulation exists regarding these biohazards. Nevertheless, considering their low infective dose, ingestion of foodstuffs contaminated by low quantities of these three parasites can lead to human infection. To evaluate the risk of protozoan parasites in food, efforts must be made towards exposure assessment to estimate the contamination along the food chain, from raw products to consumers. This requires determining: (i) the occurrence of infective protozoan (oo)cysts in foods, and (ii) the efficacy of control measures to eliminate this contamination. In order to conduct such assessments, methods for identification of viable (i.e. live) and infective parasites are required. This review describes the methods currently available to evaluate infectivity and viability of G. duodenalis cysts, Cryptosporidium spp. and T. gondii oocysts, and their potential for application in exposure assessment to determine the presence of the infective protozoa and/or to characterize the efficacy of control measures. Advantages and limits of each method are highlighted and an analytical strategy is proposed to assess exposure to these protozoa.

Improving chemical risk assessment through tiered and targeted application of exposure assessment

Improving chemical risk assessment through tiered and targeted application of exposure assessment

Sampling Conventions for Estimating Ultrafine and Fine Aerosol Particle Deposition in the Human Respiratory Tract

To provide targets for personal samplers designed for estimating particle deposition at distinct locations in the body, accounting if necessary for inter- and intra-person variation. Ultrafine and fine aerosol sampling conventions are proposed for approximating the deposition efficiency for five distinct loci of the respiratory tract. The 2 × 5 = 10 conventions represent averages over variation in physical activity level, posture, sex, and breathing mode. Recognizing three approximate relationships among the 10 deposition efficiencies, the number of independent conventions is reduced to only seven, namely three ultrafine and four fine aerosol conventions. The ultrafine and fine conventions are defined as ideal sampling efficiencies in terms of thermodynamic (independent of particle density) and aerodynamic diameter, respectively. Addition of measured mass, surface area, or particle count from aerosol collected by sampler pairs in agreement with convention can be used to estimate dose (prior to clearance) at a particular locus in the mean over breathing conditions ranging from sitting, to light, or to heavy exercise, normal or mouth breathing, and male or female, with aerosol density effects partially corrected automatically by the separate aerodynamic and thermodynamic sampling. Linear combinations of the conventions can be used for yet simpler sampling, though with limited distinctness as to deposition locus. Alternatively to estimating simply a mean, the large inter- and intra-person variation (relative standard deviation of the order of 100%) corresponding to the wide range of breathing conditions can be approximately corrected by using 'arrays' of samplers in agreement with convention, given suitable profiling of the individual whose dose is to be assessed. The intent behind the proposed conventions is not to eliminate the current aerosol penetration conventions, which have found international application in exposure assessment particularly for determining compliance with standards on acceptable aerosol levels. The aim is to promote personal sampler design leading to more sharply defined health research than can be done at present.

A scanning transmission electron microscopy method for determination of manganese composition in welding fume as a function of primary particle size

Increasing evidence suggests that the physicochemical properties of inhaled nanoparticles influence the resulting toxicokinetics and toxicodynamics. This report presents a method using scanning transmission electron microscopy (STEM) to measure the Mn content throughout the primary particle size distribution of welding fume particle samples collected on filters for application in exposure assessment and health research. Dark field images were collected to assess the primary particle size distribution and energy-dispersive X-ray and electron energy loss spectroscopy were performed for measurement of Mn composition as a function of primary particle size. A manual method incorporating imaging software was used to measure the primary particle diameter and to select an integration region for compositional analysis within primary particles throughout the size range. To explore the variation in the developed metric, the method was applied to 10 gas metal arc welding (GMAW) fume particle samples of mild steel that were collected under a variety of conditions. The range of Mn composition by particle size was −0.10 to 0.19%/nm, where a positive estimate indicates greater relative abundance of Mn increasing with primary particle size and a negative estimate conversely indicates decreasing Mn content with size. However, the estimate was only statistically significant ( p<0.05) in half of the samples ( n=5), which all had a positive estimate. In the remaining samples, no significant trend was measured. Our findings indicate that the method is reproducible and that differences in the abundance of Mn by primary particle size among welding fume samples can be detected.

Analysis of Temporal and Spatial Variability in Disinfection By-product Concentrations for Exposure Assessment Applications

PP-30-118 Background/Aims: Most epidemiological studies of disinfection by-products rely on aggregate water system average total trihalomethane (TTHM) and total haloacetic acid concentrations as surrogate measures for individual-level exposure. It is critical that these surrogates accurately reflect temporal and spatial variability in disinfection by-product concentrations to reduce exposure misclassification. Methods: We assessed temporal and spatial variability in routinely collected TTHM monitoring data for 201 public water systems (PWSs) in Massachusetts from 1995 to 2004. Results: The annual TTHM average across 46 PWSs with complete quarterly data remained relatively unchanged during the study period (1995: 41.3 μg/L; 2004: 42.4 μg/L). However, average TTHM among systems disinfecting with chloramination (n = 5 PWSs) increased considerably (1995: 23.6 μg/L; 2004: 43.0 μg/L), while TTHM levels increased slightly among chlorinated systems (n = 30 PWSs). The quarterly averages across 46 PWSs showed consistent seasonality with a 30%–50% higher summer average TTHM compared to winter. High spatial variability (ie, ≥1 sampling date with TTHM between-location differences was ≥30 μg/L) was noted in 49% of PWSs. Over half of these PWSs had high spatial variability for at least 25% of their sampling dates. We also examined spatial variability based on different disinfection practices for 4 PWSs that used chloramination at some point during the study period. Among these systems, 64% of the chlorinated sample dates had high spatial variability compared to 1% of the chloraminated sample dates reported. Conclusion: Our seasonal variability findings emphasize the need for quarterly sampling dates to adequately capture short-term temporal trends. We found considerable spatial variability across several water systems, which could result in misclassification bias if system averages are used to estimate individual-level TTHM and THAA exposures. Therefore, exposure assessment approaches should target systems with minimal spatial variability and sensitivity analyses should examine potential exposure misclassification in larger epidemiological studies based on water systems using different types of disinfectants.

An Analysis of Spatial Variability in Disinfection By-Product Concentrations for Exposure Assessment Applications

An Analysis of Spatial Variability in Disinfection By-Product Concentrations for Exposure Assessment ApplicationsMany epidemiological studies of disinfection by-products (DBPs) rely on aggregatewater system average trihalomethane (i.e., THM4: sum of chloroform, dibromochloromethane, bromodichloromethane and bromoform) and haloacetic acid (i.e., HAA5: sum of monochloroacetic acid, dichloroacetic acid, trichloroacetic acid, monobromoacetic acid and dibromoacetic acid) concentrations as surrogate measures for...Author(s)Amanda EvansAmy MeyerZorimar Rivera-NúñezJ. Michael WrightSourceProceedings of the Water Environment FederationSubjectSession 5: Emerging Impacts of Chlorine DisinfectionDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2011ISSN1938-6478SICI1938-6478(20110101)2011:3L.172;1-DOI10.2175/193864711802863724Volume / Issue2011 / 3Content sourceDisinfection and Reuse SymposiumFirst / last page(s)172 - 179Copyright2011Word count460Subject keywordsDisinfection by-productsexposure assessmentexposure misclassificationspatial variabilitydrinking water

Use of land surface remotely sensed satellite and airborne data for environmental exposure assessment in cancer research.

In recent years, geographic information systems (GIS) have increasingly been used for reconstructing individual-level exposures to environmental contaminants in epidemiological research. Remotely sensed data can be useful in creating space-time models of environmental measures. The primary advantage of using remotely sensed data is that it allows for study at the local scale (e.g., residential level) without requiring expensive, time-consuming monitoring campaigns. The purpose of our study was to identify how land surface remotely sensed data are currently being used to study the relationship between cancer and environmental contaminants, focusing primarily on agricultural chemical exposure assessment applications. We present the results of a comprehensive literature review of epidemiological research where remotely sensed imagery or land cover maps derived from remotely sensed imagery were applied. We also discuss the strengths and limitations of the most commonly used imagery data (aerial photographs and Landsat satellite imagery) and land cover maps.

Campylobacter source attribution by exposure assessment

A new application of exposure assessment aimed at improving insight into source attribution of human infectious diseases, i.e. estimation of the relative contribution of sources and transmission routes, is developed and explored. Human exposure, calculated as the mean number of Campylobacters ingested per person per day, is used as an indication of the relative importance of Campylobacter transmission routes in the Netherlands. Thirty-one routes were investigated, related to ingestion of food, direct contact with animals and water. Preliminary results suggest that raw food consumption and direct contact are significant transmission routes, but huge data gaps exist and no solid conclusions can be drawn. More data will have to be obtained to reduce uncertainty and thereby make this tool applicable for source attribution. Methodological improvements are necessary to take the step to numbers of cases as model output and thereby to risk assessment.

Effects of vibration on grip and push force-recall performance

Comprehensive assessments of health risks associated with the operation of vibratory tools should include evaluations of hand–tool coupling forces. The use of hand-force instrumentation in field applications can be difficult and expensive. A previous study (McDowell, T.W., Wiker, S.F., Dong, R.G., Welcome, D.E., Schopper, A.W., 2006. Evaluation of psychometric estimates of vibratory hand–tool grip and push forces. International Journal of Industrial Ergonomics 36(2), 119–128.) examined various combinations of handle vibration frequencies and grip and push force levels upon one's ability to recall those forces using psychophysical methods. The results of that study were promising. The present study is a follow-up experiment that further investigated the potential for using psychophysical force-recall methods to estimate grip and push forces when operating powered hand tools. In this experiment, 20 subjects (10 male, 10 female) grasped and pushed an instrumented handle for 45 s at one of three force levels while it vibrated sinusoidally at one of four frequencies (16, 31.5, 63, or 125 Hz) or with no vibration. Unlike the first study, two levels of vibration magnitude were examined along with gender differences. This study further clarifies relationships between vibration exposure characteristics and their effects on grip and push force-recall performance. Vibration exposure conditions and other influential factors can be accounted for in enhanced force-recall methodologies that can be incorporated into a variety of workplace exposure assessment applications. Relevance to industry Workers who are repeatedly exposed to intense hand-transmitted vibration are at risk of developing health problems. To better assess these health risks, hand–tool coupling forces should be evaluated. A refined psychophysical force-recall technique may be a practical alternative to expensive or fragile instrumentation. Before such a method is proposed for laboratory or field applications, an understanding of vibration effects upon force-recall performance must first be explored.

The Major Themes from the Plenary Panel Session of the International Society of Exposure Analysis — 2004 Annual Meeting on: The Application of Exposure Assessment to Environmental Health Science and Public Policy — What has been Accomplished and What Needs to Happen before Our 25th Anniversary in 2014

The Major Themes from the Plenary Panel Session of the International Society of Exposure Analysis — 2004 Annual Meeting on: The Application of Exposure Assessment to Environmental Health Science and Public Policy — What has been Accomplished and What Needs to Happen before Our 25th Anniversary in 2014

Overview of Fish Consumption Rates in the United States

ABSTRACT Contaminants that accumulate in fish may pose health risks and have raised concerns among consumers. Contaminated finfish and shellfish are possible routes of human exposure to toxic chemicals. Fish advisories are established to protect local populations from the consumption of contaminated commercial and non-commercially caught fish. Children, women of childbearing age, and subsistence fishermen or other highly exposed individuals who for socioeconomic or cultural reasons consume more fish than the general population are among the populations of concern from the ingestion of contaminated fish. Estimating exposure to a toxic chemical among fish-consuming populations requires knowledge about intake rates of fish and shellfish. Data on fish consumption rates come from various sources, including national, state, and local government studies. Although these data have their limitations, they serve as a source for deriving fish consumption rates that may be used by exposure assessors. Data on specific populations of concern are critical. Studies presented here show that ethnicity, age, and geographical region play an important role in fishing behavior and consumption. Results from studies on Native American populations show that this ethnic group eats fish at a higher rate than recreational anglers. This article summarizes data on fish consumption for various populations and provides a framework for evaluating data from these studies for exposure assessment applications.

Sampling environments containing organic dust

Assessment of airborne organic dust in different environments is necessary to better understand the relationship between exposure and disease. Exposure assessment requires a well-defined sampling strategy which addresses the following questions: Where, how long, who, how many, and when? For assessing exposure to organic dust, the question of "what?" must be included because, in most cases, the specific toxins or appropriate surrogates for exposure have not been identified. For most environments with organic dust, these questions have not been adequately addressed. However, a large database exists for cotton dust. Cotton is used as a model of organic dust to illustrate the application of exposure assessment: 1) to develop a dose-response relationship between aerosolized dust and specific health effects; 2) to evaluate the effects of process change on gravimetric dust levels and for compliance with the cotton dust standard; and 3) to identify specific biologically active components in the dust.

Power frequency magnetic fields in the home

The methodology and findings of a domestic magnetic field measurement program are presented. The purpose was to improve understanding of power-frequency magnetic fields in typical domestic locations for exposure assessment applications. Spot measurements were made at ninety-one sites in six states. In addition, twenty-four-hour continuous measurements were made at a few homes. The household magnetic fields are highly variable and exhibit diurnal cycles. Results suggest that the statistical distributions of magnetic field measurements follow a lognormal probability model. Typical mean values of the resultant in most rooms for these data are about 1 mG, with a standard deviation of about twice the mean peak values of 12 mG. Measurements taken during use of appliances are much higher and have resultant means of about 9-20 mG, with standard deviations of about 40-75 mG and some peak values exceeding 1000 mG. >