Nanometer-sized emissions from municipal waste incinerators: A qualitative risk assessment

Municipal waste incinerators (MWI) are beneficial alternatives to landfills for waste management. A recent constituent of concern in emissions from these facilities is incidental nanometer-sized particles (INP_MWI), i.e., particles smaller than 1 micrometer in size that may deposit in the deepest parts of the lungs, cross into the bloodstream, and affect different regions of the body. With limited data, the public may fear INP_MWI due to uncertainty, which may affect public acceptance, regulatory permitting, and the increased lowering of air quality standards. Despite limited data, a qualitative risk assessment paradigm can be applied to determine the relative risk due to INP_MWI emissions. This review compiles existing data on nanometer-sized particle generation by MWIs, emissions control technologies used at MWIs, emission releases into the atmosphere, human population exposure, and adverse health effects of nanometer-sized particles to generate a qualitative risk assessment and identify data gaps. The qualitative risk assessment conservatively concludes that INP_MWI pose a low to moderate risk to individuals, primarily due to the lack of relevant toxicological data on INP_MWI mixtures in ambient particulate matter.

Particle Size Distribution in Aluminum Manufacturing Facilities

As part of exposure assessment for an ongoing epidemiologic study of heart disease and fine particle exposures in aluminum industry, area particle samples were collected in production facilities to assess instrument reliability and particle size distribution at different process areas. Personal modular impactors (PMI) and Minimicro-orifice uniform deposition impactors (MiniMOUDI) were used. The coefficient of variation (CV) of co-located samples was used to evaluate the reproducibility of the samplers. PM2.5 measured by PMI was compared to PM2.5 calculated from MiniMOUDI data. Mass median aerodynamic diameter (MMAD) and concentrations of sub-micrometer (PM1.0) and quasi-ultrafine (PM0.56) particles were evaluated to characterize particle size distribution. Most of CVs were less than 30%. The slope of the linear regression of PMI_PM2.5 versus MiniMOUDI_PM2.5 was 1.03 mg/m3 per mg/m3 (± 0.05), with correlation coefficient of 0.97 (± 0.01). Particle size distribution varied substantively in smelters, whereas it was less variable in fabrication units with significantly smaller MMADs (arithmetic mean of MMADs: 2.59 μm in smelters vs. 1.31 μm in fabrication units, p = 0.001). Although the total particle concentration was more than two times higher in the smelters than in the fabrication units, the fraction of PM10 which was PM1.0 or PM0.56 was significantly lower in the smelters than in the fabrication units (p < 0.001). Consequently, the concentrations of sub-micrometer and quasi-ultrafine particles were similar in these two types of facilities. It would appear, studies evaluating ultrafine particle exposure in aluminum industry should focus on not only the smelters, but also the fabrication facilities.