Use of Personal-Indoor-Outdoor Sulfur Concentrations to Estimate the Infiltration Factor and Outdoor Exposure Factor for Individual Homes and Persons
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- 作者：Lance Wallace and Ron Williams
- 刊名：Environmental Science & Technology
- 出版年：2005
- 出版时间：March 15, 2005
- 年：2005
- 卷：39
- 期：6
- 页码：1707 - 1714
- 全文大小：167K
- 年卷期：v.39,no.6(March 15, 2005)
- ISSN：1520-5851
文摘
A study of personal, indoor, and outdoor exposure toPM2.5 and associated elements has been carried out for37 residents of the Research Triangle Park area in NorthCarolina. Participants were selected from persons expectedto be at elevated risk from exposure to particles, andincluded 29 persons with hypertension and 8 cardiac patientswith implanted defibrillators. Participants were monitoredfor 7 consecutive days in each of four seasons. Onegoal of the study was to estimate the contribution of outdoorPM2.5 to indoor concentrations. This depends on theinfiltration factor Finf, the fraction of outdoor PM2.5 remainingairborne after penetrating indoors. After confirming withour measurements the findings of previous studies that sulfurhas few indoor sources, we estimated an average Finffor each house based on indoor/outdoor sulfur ratios. Theseestimates ranged from 0.26 to 0.87, with a median valueof 0.55. Since these estimates apply only to particles of sizesimilar to that of sulfur particles (0.06-0.5 
tities/mgr.gif">m diameter),and since larger particles (0.5-2.5 tities/mgr.gif">m) have lower penetrationrates and higher deposition rates, these estimates arelikely to be higher than the true infiltration factors for PM2.5as a whole. In summer when air conditioners were inuse, the sulfur-based infiltration factor was at its lowest(averaging 0.50) for most homes, whereas the average Finffor the other three seasons was 0.62-0.63. Using thedaily estimated infiltration factor for each house, we calculatedthe contribution of outdoor PM2.5 to indoor air concentrations.The indoor-generated contributions to indoor PM2.5 hada wider range (0-33 tities/mgr.gif">g/m3) than the outdoor contributions(5-22 tities/mgr.gif">g/m3). However, outdoor contributions exceededthe indoor-generated contributions in 27 of 36 homes. Asecond goal of the study was to determine the contributionof outdoor particles to personal exposure. This is determinedby the "outdoor exposure factor" Fpex, the fraction ofoutdoor PM2.5 contributing to personal exposure. As withFinf, we estimated Fpex by the personal/outdoor sulfur ratios.The estimates ranged from 0.33 to 0.77 with a medianvalue of 0.53. Outdoor air particles were less importantfor personal exposures than for indoor concentrations, withthe median outdoor contribution to personal exposurejust 49%. We regressed the outdoor contributions to personalexposures on measured outdoor PM2.5 at the centralsite. The regressions had R2 values ranging from 0.19 to0.88 (median = 0.73). These values provide an indicationof the extent of misclassification error in epidemiologicalestimates of the effect of outdoor particles on health.
tities/mgr.gif">m diameter),and since larger particles (0.5-2.5 tities/mgr.gif">m) have lower penetrationrates and higher deposition rates, these estimates arelikely to be higher than the true infiltration factors for PM2.5as a whole. In summer when air conditioners were inuse, the sulfur-based infiltration factor was at its lowest(averaging 0.50) for most homes, whereas the average Finffor the other three seasons was 0.62-0.63. Using thedaily estimated infiltration factor for each house, we calculatedthe contribution of outdoor PM2.5 to indoor air concentrations.The indoor-generated contributions to indoor PM2.5 hada wider range (0-33 tities/mgr.gif">g/m3) than the outdoor contributions(5-22 tities/mgr.gif">g/m3). However, outdoor contributions exceededthe indoor-generated contributions in 27 of 36 homes. Asecond goal of the study was to determine the contributionof outdoor particles to personal exposure. This is determinedby the "outdoor exposure factor" Fpex, the fraction ofoutdoor PM2.5 contributing to personal exposure. As withFinf, we estimated Fpex by the personal/outdoor sulfur ratios.The estimates ranged from 0.33 to 0.77 with a medianvalue of 0.53. Outdoor air particles were less importantfor personal exposures than for indoor concentrations, withthe median outdoor contribution to personal exposurejust 49%. We regressed the outdoor contributions to personalexposures on measured outdoor PM2.5 at the centralsite. The regressions had R2 values ranging from 0.19 to0.88 (median = 0.73). These values provide an indicationof the extent of misclassification error in epidemiologicalestimates of the effect of outdoor particles on health.