title: Comparing exposure zones by different exposure metrics using statistical parameters: contrast and precision.
abstract: Recently, the appropriateness of using the 'mass concentration' metric for ultrafine particles has been questioned and surface area (SA) or number concentration metrics has been proposed as alternatives. To assess the abilities of various exposure metrics to distinguish between different exposure zones in workplaces with nanoparticle aerosols, exposure concentrations were measured in preassigned 'high-' and 'low-'exposure zones in a restaurant, an aluminum die-casting factory, and a diesel engine laboratory using SA, number, and mass concentration metrics. Predetermined exposure classifications were compared by each metric using statistical parameters and concentration ratios that were calculated from the different exposure concentrations. In the restaurant, SA and fine particle number concentrations showed significant differences between the high- and low-exposure zones and they had higher contrast (the ratio of between-zone variance to the sum of the between-zone and within-zone variances) than mass concentrations. Mass concentrations did not show significant differences. In the die cast facility, concentrations of all metrics were significantly greater in the high zone than in the low zone. SA and fine particle number concentrations showed larger concentration ratios between the high and low zones and higher contrast than mass concentrations. None of the metrics were significantly different between the high- and low-exposure zones in the diesel engine laboratory. The SA and fine particle number concentrations appeared to be better at differentiating exposure zones and finding the particle generation sources in workplaces generating nanoparticles. Because the choice of an exposure metric has significant implications for epidemiologic studies and industrial hygiene practice, a multimetric sampling approach is recommended for nanoparticle exposure assessment.
authors.affiliation: University of Minnesota, Minneapolis, 55455, USA.
authors.forename: Ji Young
authors.initials: JY
authors.lastname: Park
authors.forename: Gurumurthy
authors.initials: G
authors.lastname: Ramachandran
authors.forename: Peter C
authors.initials: PC
authors.lastname: Raynor
authors.forename: Lynn E
authors.initials: LE
authors.lastname: Eberly
authors.forename: Greg
authors.initials: G
authors.lastname: Olson
mesh_terms: D000336:Aerosols / Q000032:analysis; D000395:Air Pollutants, Occupational / Q000032:analysis*; D000535:Aluminum / Q000032:analysis; D000704:Analysis of Variance; D003296:Cooking; D004784:Environmental Monitoring / Q000379:methods* / Q000706:statistics & numerical data; D006801:Humans; D007753:Laboratories; D016014:Linear Models; D053758:Nanoparticles / Q000032:analysis*; D016273:Occupational Exposure / Q000032:analysis / Q000706:statistics & numerical data*; D012016:Reference Values; D012107:Research Design; D013499:Surface Properties; D014691:Ventilation; D017132:Workplace / Q000706:statistics & numerical data
chemical_list: D000336:Aerosols; D000395:Air Pollutants, Occupational; D000535:Aluminum