USC study shows large pol­lu­tion ex­po­sure re­duc­tions pos­si­ble with car ven­ti­la­tion set­ting choices

Wellness Update - - Contents -


Based on a new study, en­vi­ron­men­tal health re­searchers at the Univer­sity of South­ern Cal­i­for­nia have ad­vice for par­ents who want to re­duce their child’s ex­po­sure to harm­ful traf­fic pol­lu­tants: The car ven­ti­la­tion choice you make can be ef­fec­tive in re­duc­ing ex­po­sure to on-road par­ti­cle pol­lu­tion. Scott Fruin, D.Env., as­sis­tant pro­fes­sor of pre­ven­tive medicine, and Nee­lak­shi Hudda, PhD, re­search as­so­ci­ate in the en­vi­ron­men­tal health depart­ment of the Keck School of Medicine of USC, re­cently con­ducted the first sys­tem­atic mea­sure­ments of in­ve­hi­cle ex­po­sure that in­cluded a full range of car types and op­er­at­ing con­di­tions, and for all types of par­tic­u­late pol­lu­tion. “Short of driv­ing less, putting your ven­ti­la­tion to ‘re­cir­cu­late’ is the best way to re­duce ex­po­sure to all types of ve­hi­cle-re­lated par­tic­u­late pol­lu­tion,” said Fruin,

se­nior au­thor on the study. “Oth­er­wise, an hour-long com­mute to work or school can dou­ble your daily ex­po­sure to traf­fic-re­lated par­tic­u­late air pol­lu­tants.” The sci­en­tists found in ad­di­tion to the ben­e­fits of re­cir­cu­la­tion set­tings, ex­po­sures are lower in newer cars, at slower speeds, and on ar­te­rial roads, where pol­lu­tant con­cen­tra­tions are lower than on free­ways. Ac­cord­ing to the re­searchers, con­cen­tra­tions of par­ti­cle pol­lu­tants on free­ways are of­ten five to 10 times higher than else­where. To put the re­sults in per­spec­tive, mea­sure­ments were turned into pre­dic­tive mod­els, then the mod­els were ap­plied to the na­tional fleet of car mod­els and ages and Los An­ge­les driv­ing con­di­tions. Drs. Fruin and Hudda found that for a typ­i­cal car (seven years old, the na­tional av­er­age), re­cir­cu­la­tion set­tings re­duce in-ve­hi­cle par­ti­cle pol­lu­tion for very small par­ti­cles from 80 per­cent (of on-road lev­els) to 20 per­cent, and from 70 per­cent to 30 per­cent for larger par­ti­cles, com­pared to air ven­ti­la­tion set­tings which bring in out­side air. (Win­dows were al­ways closed in this study. Keep­ing win­dows open while driv­ing quickly raises in­side pol­lu­tant con­cen­tra­tions to the same lev­els as on-road lev­els.) “Un­til this com­pre­hen­sive study, mea­sure­ments have been based on only a few cars and usu­ally only one pol­lu­tant,” Hudda said. “We showed that re­cir­cu­la­tion set­tings pro­duce large ex­po­sure re­duc­tions across all car types and for all par­tic­u­late pol­lu­tants.” The re­searchers also found that leav­ing the win­dows closed over 30-minute or longer drives with sev­eral pas­sen­gers raised carbon diox­ide lev­els in tight new cars to those of stuffy meet­ing rooms.

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