Measurement Methods to Determine Compliance with Ambient Air Quality Standards for Suspended Particles

209

138

Here we compare PM 2.5 (particles with aerodynamic diameter less than 2.5 mm) mass and filter absorbance measurements with elemental carbon (EC) concentrations measured in parallel at the same site as well as collocated PM 2.5 and PM 10 (particles with aerodynamic diameter less than 10 mm) mass and absorbance measurements. The data were collected within the Traffic-Related Air Pollution on Childhood Asthma (TRAPCA) study in Germany, The Netherlands and Sweden. The study was designed to assess the health impact of spatial contrasts in long-term average concentrations. The measurement sites were distributed between background and traffic locations. Annual EC and PM 2.5 absorbance measurements were at traffic sites on average 43-84% and 26-76% higher, respectively, compared to urban background sites. The contrast for PM 2.5 mass measurements was lower (8-35%). The smaller contrast observed for PM 2.5 mass in comparison with PM 2.5 absorbance and EC documents that PM 2.5 mass underestimates exposure contrasts related to motorized traffic emissions. The correlation between PM 10 and PM 2.5 was high, documenting that most of the spatial variation of PM 10 was because of PM 2.5 . The measurement of PM 2.5 absorbance was highly correlated with EC measurements and suggests that absorbance can be used as a simple, inexpensive and non-destructive method to estimate motorized traffic-related particulate air pollution. The EC/absorbance relation differed between countries and site type (background/traffic), supporting the need for site-specific calibrations of the simple absorbance method. While the ratio between PM 2.5 and PM 10 mass ranged from 0.54 to 0.68, the ratio of PM 2.5 absorbance and PM 10 absorbance was 0.96-0.97, indicating that PM 2.5 absorbance captures nearly all of the particle absorbance.

Section: Discussionsupporting

confidence: 78%

Comparison between different traffic-related particle indicators: Elemental carbon (EC), PM2.5 mass, and absorbance

Cyrys

Heinrich

Hoek

et al. 2003

209

138

“…BS is measured by light absorbance of exposed filters and is mostly related to elemental carbon emissions from diesel engines, whereas NO 2 reflects emissions from all motorized vehicles. BS is not a good proxy for PM 10 or PM 2.5 , but is highly correlated with the elemental carbon content of particles (Edwards et al, 1983;Chow, 1995;Janssen et al, 2001 ). Therefore, it is a more direct indicator of exposure to ( diesel ) traffic-related particles than PM 10 or PM 2.5 .…”

Section: Pollutantsmentioning

confidence: 97%

Estimation of long-term average exposure to outdoor air pollution for a cohort study on mortality

Hoek

Fischer

Brandt

et al. 2001

137

Recent prospective cohort studies have suggested that long -term exposure to low levels of particulate matter ( PM ) air pollution is associated with increased mortality due to, especially, cardio -pulmonary disease. Exposure to ambient air pollution was estimated mostly as city average concentrations, assuming homogenous exposure within the city. We used an ongoing cohort study -The Netherlands Cohort Study ( NLCS ) on diet and cancer -to investigate the relationship between traffic -related air pollution and mortality. The baseline data collection took place in 1986. A study was conducted to develop methods for exposure assessment and evaluate the contrast in exposure to air pollution within the cohort. Assessment of long -term exposure to two traffic -related air pollutants, Black Smoke ( BS ) and Nitrogen Dioxide ( NO 2 ) , consisted of separate estimation of regional background, urban background, and local traffic contributions at the home address. Interpolation of concentration data from a routine monitoring network was used to estimate the regional background concentration. A regression model relating degree of urbanization to air pollution was used to allow for differences between different towns / neighborhoods of cities. Distance to major roads was calculated to characterize local traffic contributions, using a Geographic Information System ( GIS ) . Interpolation resulted in reasonably precise regional background estimation when distant sites were not used and distance squared was used as the weight. Cross -validation showed that prediction errors were about 15% of the range in regional background concentration. Urban and local scales contributed significantly to the contrast within the cohort. Prediction errors for estimating the urban background were about 25% of the range in background concentrations. When the developed model was applied to the study cohort, there was substantial contrast in estimated exposure to BS and NO 2 . About 90% of the study population lived 10 years or more at its 1986 home address -supporting the use of the estimated concentration at the 1986 address as a relevant exposure variable.

“…TEOM monitors were operated at 508C to remove particlebound water from the flow stream at a flow rate of 1 l/ min. The Hi -Vol method draws air at ambient temperature through a fiber filter mounted behind a size -selective inlet for a 24 -h period at a flow rate of 1.13 m 3 /min, so that particles impact on the filter medium, and then the filter is removed and weighed in a climate -controlled room (Chow, 1995 ).…”

Section: Pm 10 Datamentioning

confidence: 99%

“…In addition, although particle monitors may be designated as ''equivalent'' to the Federal Reference Method sampler in the US (Chow, 1995 ), the field conditions under which these methods are deemed equivalent may not reflect circumstances in other parts of the world, where different climatic patterns, particle compositions, and/ or operating protocols may exist. Some meta -analyses of particle /mortality epidemiology studies have addressed the issue of different measurement methods by converting exposure metrics provided in units other than PM 10 [e.g., total suspended particles (TSPs ), or Coefficient of Haze ] to PM 10 , applying data -derived correction factors (Ostro, 1993;Dockery and Pope, 1994;Levy et al, 2000 ).…”

Section: Introductionmentioning

confidence: 99%

Estimating particle exposure in the Mexico City metropolitan area

OʼNeill

Loomis

Meza

et al. 2002

Study question: We examined whether methods for measuring exposure to airborne particles less than 10 m in aerodynamic diameter ( PM 10 ) in the Mexico City metropolitan area give different estimates of PM 10 levels, and the nature of these differences, and developed a model for estimating missing PM 10 data for one measurement method. Methods: Government PM 10 measurements using two different technologies at five sites ( the Sierra -Anderson PM 10 HighVolume Air Sampler System, Hi -Vol ) ( every sixth day ) and the Rupprecht and Patashnik Tapered Element Oscillating Microbalance ( TEOM ) monitor ( daily ), as well as Harvard Impactor ( HI ) data collected for research purposes from one monitoring station were matched by day and monitoring site, then compared visually and with basic descriptive statistics. We fit linear regression models with airport visual range measurements, meteorological data, and information on other air pollutants to predict the Hi -Vol measured PM 10 levels for those days when direct measurements were not available. Results: We found relatively low correlations ( r ranging from 0.46 to 0.63 ) between PM 10 measured with the TEOM and Hi -Vol methods, and highly variable differences ( 0 -70 g / m 3 ) between the means of these measurements, depending on monitoring site. The HI measurements had a relatively high correlation with the Hi -Vol measurements ( r = 0.90 ). The models developed for the missing Hi -Vol measurements provided a series of estimated values similar to the actual Hi -Vol measurements, although the estimated series did not have high values in the range observed in the measured data. Conclusions: The differences we observed in the PM 10 measurements across methods in Mexico City may be important when studying health effects associated with particle exposure, evaluating method performance under conditions and operating protocols similar to those in Mexico City, and determining compliance with air quality standards. The estimated series of PM 10 measures may be a useful index of exposure for use in studies of the effects of air pollution on health.