Evaluation of 1-Nitropyrene as a Surrogate Measure for Diesel Exhaust.

We investigated the viability of particle bound 1-nitropyrene (1-NP) air concentration measurements as a surrogate of diesel exhaust (DE) exposure, as compared with industry-standard elemental carbon (EC) and total carbon (TC) measurements. Personal exposures are reported for 18 employees at a large underground metal mine during four different monitoring campaigns. Full-shift personal air exposure sampling was conducted using a Mine Safety and Health Administration (MSHA) compliant diesel particulate matter (DPM) impactor cassette downstream of a GS-1 cyclone pre-selector. Each DPM filter element was analyzed for EC and organic carbon (OC) using NIOSH Method 5040. After EC and OC analysis, the remaining portion of each DPM filter was analyzed for 1-NP using liquid chromatography tandem mass spectrometry (LC/MS/MS). We observed high correlations between the quantiles of 1-NP and EC exposures across 10 different work shift task groups (r = 0.87 to 0.96), and a linear relationship with a slope between 6.0 to 6.9 pg 1-NP per µg EC. However, correlation between 1-NP and EC was weak (r =0.34) for the 91 individual sample pairs due to low EC concentrations and possible heterogeneity of DE composition. While both 1-NP and EC differentiated between high and low exposure groups categorized by job location, measurements of 1-NP, but not EC further differentiated between specific job activities. Repeated measurements on individual subjects verified the relationship between 1-NP and EC and demonstrated substantial within-subject variability in exposure. The detection limit of TC air concentration ranged between 18 and 28 µg m-3 and was limited by OC contamination of the quartz filters in the MSHA compliant DPM samplers.

Side-by-side comparison of three sampling methods for aerosolized endotoxin in a wastewater treatment facility.

Research studies have established the occurrence of adverse health effects in individuals exposed to organic dusts and water aerosols laden with endotoxin. To determine what exposure levels cause these health effects, it is necessary to quantify airborne endotoxin. Several scientific studies have demonstrated that the quantification of detectable endotoxin is affected by differences in sampling media, analytical method, and aerosol composition. The study reported here performed side-by-side endotoxin sampling using a liquid impinger, a glass fiber filter, and a polycarbonate filter in a wastewater treatment plant. Results show levels of detected endotoxin appear to be highest with the impinger. Coefficients of variation calculated for each sampling method show the glass fiber filter having the least variability when sampling was conducted at the highest endotoxin levels. Lastly, a Spearman rank order correlation test identified an apparent correlation between endotoxin levels obtained with the impinger and the glass fiber filter.