Uncertainty estimation of exposure factors for consumer products based on various sample sizes.

Usage patterns of consumer products (CP) must be determined for accurate exposure assessments. The purpose was to quantitatively estimate the uncertainty in exposure factors of CP according to various sample sizes. The uncertainty was calculated based on exposure factors of 3,333 participants representing the Korean population referred to as the 'parent population'. Small subsamples of participants randomly selected from the parent population were used to evaluate the exposure factors of 13 CPs. Exposure factors were compared with the corresponding values from the parent population. For all exposure factors, the ratio of the mean values of the 75th percentile of the subsamples to the values of the parent population became closer to 1 as the subsample size increased. For frequency of use factor, the ratio was between 0.9 and 1.1 with sample size of 100 except household bleach and trigger-type bathroom cleaner. For amount of use factor, the ratio was between 0.9 and 1.1 with sample size of 100 except body wash, household bleach, and glass cleaner. These results showed the quantitative uncertainty of exposure factor estimations according to various sample sizes. A sample size of at least 100 subjects should be collected for estimation of exposure factors for most CP.

Characteristics of Indoor PM2.5 Concentration in Gers Using Coal Stoves in Ulaanbaatar, Mongolia.

Coal combustion in ger areas is the main source of ambient air pollution in Ulaanbaatar (Mongolia). This study determined the characteristics of indoor PM2.5 concentrations in gers using coal stoves during winter. The study population consisted of 60 gers in the Chingeltei district of Ulaanbaatar. The indoor particle number concentration (PNC) in each ger was measured using a Dylos DC1700 particle counter for 24 h in January and February 2016. The PNC by Dylos was converted into the mass concentration using a calibration equation developed using a collocated real-time light scattering monitor adjusted by gravimetric measurement. The average 24 h PM2.5 concentration was 203.9 ± 195.1 µg/m³ in gers with traditional stoves (n = 29) and 257.5 ± 204.4 µg/m³ in those with improved stoves (n = 31). In the daily profile, concentrations were lower at night, increased in the early morning, and peaked up to noon. The temperature in gers was slightly higher than that recommended in winter. Many development-assistance programs have supported the installation of improved energy-efficient stoves. Better control measures are needed to improve the indoor air quality of gers.

Impact of exposure factor selection on deterministic consumer exposure assessment.

Deterministic exposure assessment has uncertainty about the selection of input parameters on the resulting estimates. The purpose of this study was to compare inhalation exposures estimated by a specific percentile of each of the three exposure factors in deterministic assessment with population exposure. Exposure to nine household care products, namely a deodorizer, six cleaning products, and two disinfectants were investigated. The population exposures were individually calculated for three exposure factors (frequency of use, amount of use, and duration of use) from an existing database of 3333 participants representing the national population. Deterministic exposure assessment was conducted according to various percentiles of exposure factors. 99th percentiles of population exposure in all nine consumer products were 1.3-2.4 times greater than the 95th percentiles. Inhalation exposures based on the 75th percentiles of each of the three exposure factors in deterministic assessment were much lower than the 95th percentiles of the population exposure. Deterministic exposure estimates using 85th to 99th percentiles of each of the three exposure factors were closer to the 95th percentiles of the population exposure. We concluded that exposure factors in deterministic assessment should be greater than the 75th percentile to more precisely estimate exposure of at-risk groups.

Impact of Partial and Comprehensive Smoke-Free Regulations on Indoor Air Quality in Bars.

In Korea, smoke-free regulations have been gradually implemented in bars based on venue size. Smoking bans were implemented in 2013 for bars ≥150 m², in 2014 for bars ≥100 m², and in 2015 for bars of all sizes. The purpose of this study was to determine indoor fine particle (PM2.5) concentrations in bars before and after implementation of the smoke-free policies based on venue size. Indoor PM2.5 concentrations were measured with real-time aerosol monitors at four time points: (1) pre-regulation (n = 75); (2) after implementing the ban in bars ≥150 m² (n = 75); (3) after implementing the ban in bars ≥100 m² (n = 107); and (4) when all bars were smoke-free (n = 79). Our results showed that the geometric mean of the indoor PM2.5 concentrations of all bars decreased from 98.4 µg/m³ pre-regulation to 79.5, 42.9, and 26.6 µg/m³ after the ban on smoking in bars ≥150 m², ≥100 m², and all bars, respectively. Indoor PM2.5 concentrations in bars of each size decreased only after the corresponding regulations were implemented. Although smoking was not observed in Seoul bars after smoking was banned in all bars, smoking was observed in 4 of 21 bars in Changwon. Our study concludes that the greatest decrease in PM2.5 concentrations in bars was observed after the regulation covering all bars was implemented. However, despite the comprehensive ban, smoking was observed in bars in Changwon. Strict compliance with the regulations is needed to improve indoor air quality further.