Juan P. Ramos-Bonilla

Assessment of heterogeneity of metal composition of fine particulate matter collected from eight U.S. counties using principal component analysis

The main objectives of this study are to (1) characterize chemical constituents of particulate matter (PM) and (2) compare overall differences in PM collected from eight U.S. counties. This project was undertaken as a part of a larger research program conducted by the Johns Hopkins Particulate Matter Research Center (JHPMRC). The goal of the JHPMRC is to explore the relationship between health effects and exposure to ambient PM of differing composition. The JHPMRC collected weekly filter-based ambient fine particle samples from eight U.S. counties between January 2008 and January 2010. Each sampling effort consisted of a 5–6-week sampling period. Filters were analyzed for 25 metals using inductively coupled plasma mass spectrometry (ICP-MS). Overall compositional differences were ranked by principal component analysis (PCA). The results showed that weekly concentrations of each element varied 3–40 times between the eight counties. PCA showed that the first five principal components explained 85% of the total variance. The authors found significant overall compositional differences in PM as the average of standardized principal component scores differed between the counties. These findings demonstrate PCA is a useful tool to identify the differences in PM compositional mixtures by county. These differences will be helpful for epidemiological and toxicological studies to help explain why health risks associated with PM exposure are different in locations with similar mass concentrations of PM. Implications: Previous studies have demonstrated associations between health effects and particulate matter (PM) using a single component or a combination of few components. Other studies have shown constituents of PM can vary greatly by location and that these differences may explain why the health effects associated with PM exposure are different by location. However, a single or a combination of a few components cannot represent PM as a whole. To address the need for evaluating PM as a complex mixture, the authors demonstrated the utility of principal component analysis to assess heterogeneity of PM.

Personal Exposures to Asbestos Fibers During Brake Maintenance of Passenger Vehicles

INTRODUCTION Brake linings and brake pads are among the asbestos-containing products that are readily available in Colombia. When sold separated from their support, brake linings require extensive manipulation involving several steps that include drilling, countersinking, riveting, bonding, cutting, beveling, and grinding. Without this manipulation, brake linings cannot be installed in a vehicle. The manipulation process may release asbestos fibers, which may expose brake mechanics to the fibers. METHODS Three brake repair shops located in Bogotá (Colombia) were sampled for 3 or 4 consecutive days using US National Institute for Occupational Safety and Health (NIOSH) methods 7400 and 7402. Standard procedures for quality control were followed during the sampling process, and asbestos samples were analyzed by an American Industrial Hygiene Association accredited laboratory. Personal samples were collected to assess full-shift and short-term exposures. Area samples were also collected close to the brake-lining manipulation equipment and within office facilities. Activities were documented during the sampling process. RESULTS Using Phase Contrast Microscopy Equivalent counts to estimate air asbestos concentrations, all personal samples [i.e. 8-h time-weighted averages (TWAs) and 30-min personal samples] were in compliance with the US Occupational Safety and Health Administration standards. Personal asbestos concentrations based on transmission electron microscopy counts were extremely high, ranging from 0.006 to 3.493 f cm(-3) for 8-h TWA and from 0.015 to 8.835 f cm(-3) for 30-min samples. All asbestos fibers detected were chrysotile. Cleaning facilities and grinding linings resulted in the highest asbestos exposures based on transmission electron microscopy counts. There were also some samples that did not comply with the NIOSHs recommended exposure limits. CONCLUSION The results indicate that the brake mechanics sampled are exposed to extremely high asbestos concentrations (i.e. based on transmission electron microscopy counts), suggesting that this occupational group could be at excess risk of asbestos-related diseases.

Design and characterization of a sequential cyclone system for the collection of bulk particulate matter

In this paper, we describe the design, development and characterization of a high-volume sequential cyclone system for the collection of size-segregated PM in dry bulk form from the ambient environment in sufficient quantity for physical, chemical and toxicological characterization. The first stage of the system consists of a commercially available high volume PM(10) inlet. The second stage cyclone was designed by us to collect inhalable coarse particles (<10 µm and >2.5 µm). When tested individually with a challenge aerosol, a D(50) cut-size of this stage was found to be 2.3 µm at a flow rate of 1 m(3) min(-1). The third stage, a commercially available cyclone designed for surface dust sampling, had a D(50) cut-size of 0.3 µm when tested at the same flow rate. The purpose of the third stage is to collect the fine particle portion of PM(2.5) or accumulation mode (PM <2.5 µm and >0.1 µm). Thus, the sequential cyclone system will collect bulk samples of both the inhalable coarse particles and the fine particle portion of PM(2.5). The operation and maintenance of the new system are straightforward and allow for reliable collection of dry bulk ambient PM at relatively low cost.

Ambient air pollution alters heart rate regulation in aged mice.

Context: Heart rate alterations associated with exposure to particulate matter (PM) and gaseous pollutants have been observed in epidemiological studies and animal experiments. Nevertheless, the time-lag of these associations is still unclear. Objective: Determine the association at different time-lags between the complex mixture of ambient concentrations of PM, carbon monoxide (CO), and nitrogen dioxide (NO2), and markers of cardiac function in a model of aged mice. Materials and methods: AKR/J inbred mice were exposed to ambient air, 6 h daily for 40 weekdays. During this period, the animals’ electrocardiogram (ECG), deep body temperature (Tdb), and body weight (BW) were registered, and concentrations of PM, CO, NO2, as well as air temperature and relative humidity (RH) were measured. Data analysis included random effects models with lagged covariate methods. Results: CO was significantly associated with declines in heart rate (HR) and heart rate variability (HRV), PM was significantly associated with declines in HRV and BW, and NO2 was significantly associated with declines in HR. Some significant associations occurred in the same day (PM and HRV, PM and BW, CO and HR), whereas others were delayed by 1 to 3 days (CO and HR, CO and HRV, NO2 and HR, PM and HRV). Discussion and conclusion: Finding significant declines in heart function in aged mice associated with the combined effects of air pollutants at ambient concentrations and at different time-lags is of great importance to public health. These results further implicate the potential short term and delayed effects of air pollution on HR alterations.

Estimation of personal exposure to asbestos of brake repair workers.

Exposure assessments are key tools to conduct epidemiological studies. Since 2010, 28 riveters from 18 brake repair shops with different characteristics and workloads were sampled for asbestos exposure in Bogotá, Colombia. Short-term personal samples collected during manipulation activities of brake products, and personal samples collected during non-manipulation activities were used to calculate 103 8-h TWA PCM-equivalent personal asbestos concentrations. The aims of this study are to identify exposure determinant variables associated with the 8-h TWA personal asbestos concentrations among brake mechanics, and propose different models to estimate potential asbestos exposure of brake mechanics in an 8-h work-shift. Longitudinal-based multivariate linear regression models were used to determine the association between personal asbestos concentrations in a work-shift with different variables related to work tasks and workload of the mechanics, and some characteristics of the shops. Monte Carlo simulations were used to estimate the 8-h TWA PCM-Eq personal asbestos concentration in work-shifts that had manipulations of brake products or cleaning activities of the manipulation area, using the results of the sampling campaigns. The simulations proposed could be applied for both current and retrospective studies to determine personal asbestos exposures of brake mechanics, without the need of sampling campaigns or historical data of air asbestos concentrations.