The goal of this research is to evaluate the utility and predictive power of a novel technology for assessing short-term exposure to heavy metals and their link to subclinical health effects among welders. Personal exposures to both nickel (Ni) and chromium (Cr) will be quantified using a new, low-cost lung deposition sampler (LDS). The exposure estimates will then be used to investigate the individual and combined effects of these metals on oxidative DNA damage. The LDS is the first of its kind to estimate the fraction of particulate mass that deposits in the respiratory tract without the cost and weight of samplers that estimate the aerosol size distribution. The LDS has several innovative advantages: 1) It employs polyurethane foam as both the size selector and collection substrate; 2) It is inexpensive (~$1), and lightweight; 3) It operates at 4 L min-1 of flow, a condition conducive to personal sampling; 4) It allows offline trace analyses. By using a physiologically- relevant metric of particulate matter exposure, we expect that this approach will significantly reduce measurement error and improve associations between exposure and internal dose (via urine samples), while providing a feasible sampler suitable for use in large-scale studies. Personal air samples will be collected from 35 workers (8h work-shift) exposed to welding fume and metal grinding particulates on two consecutive Mondays. Concentrations of Cr and Ni will be quantified in air and urine (pre- and post-shift), and 8-hydroxy-2'- deoxyguanosine (an indicator of oxidative DNA damage) will be quantified in urine. Pearson's correlation coefficients will be used to measure the strength of association between the airborne heavy metal exposure (deposited fraction estimated by the LDS or inhalable fraction estimated by a traditional sampler) and heavy metal concentrations in urine samples. Separate general linear mixed models will be employed to predict levels of DNA damage from air exposure (LDS or traditional sampler) or urinary biomarkers, adjusting for confounders. An interaction term will be added to the DNA damage model to determine if the combined effect of exposure to Ni and Cr is greater (or less) than the additive effects of each metal independently. Innovative aspects of this study are: 1) Use of the novel LDS to provide exposure estimates that are more relevant to internal dose, 2) Use of a noninvasive exposure estimate (LDS) as a predictor of subclinical health effects (DNA damage), and 3) Simultaneous consideration of two carcinogenic heavy metals as predictors of DNA damage. This study is uniquely designed to respond to research gaps identified in the National Occupational Research Agenda (NORA, NIOSH) as: Conduct and promote exposure assessment and hazard evaluations of known and suspected carcinogens in manufacturing settings. Successful completion of the proposed aims will have two important implications: first, because occupational exposure limits are based on airborne concentrations, the LDS can improve sampling strategies to better identify workers at risk; second, the LDS can provide a physiologically representative estimate of disease risk that is more feasible than biomonitoring.
Welders are exposed to high levels of heavy metals and despite the complex nature of welding fume, few studies investigated effects of more than one pollutant. This study aims to quantify personal exposures to nickel and chromium among welders using a new, low-cost sampler that represents deposition of these heavy metals in the lung. We will evaluate whether exposure to these metals is linked to DNA damage during the workday.
