Executive SummaryRestrictions on smoking outdoors have been introduced for reasons of publicamenity and to promote litter reduction. This review considers the evidence aboutwhether outdoor secondhand smoke (SHS) might also pose health risks to others.Six published studies have assessed outdoor levels of SHS using metred PM2.5 as amarker of exposure. The magnitude of PM2.5is dependent on the number of smokerspresent, proximity of the measurement device to the source of the SHS, the extentto which the outdoor space is physically constrained (e.g., walls, partial roof,umbrellas), and wind. The data show peak outdoor PM2.5 levels in semi‐enclosedareas with several smokers present can be comparable to those recorded in indoorsmoky environments. However, outdoor PM2.5 levels are more transient as thesmoke plume is less confined and can rapidly dissipate.SHS can be a major source of PM2.5, particularly in indoor environments. The averagePM2.5 level in bars where smoking occurs is 303 μg/m3 and 157 μg/m3 in restaurants.Because of repeated and cumulative exposure to SHS in outdoor settings like beergardens and outdoor eating areas, occupational exposures to PM2.5 from SHS arelikely to be far higher than those experienced by patrons who are present for farshorter periods. We estimate that occupational exposure to SHS in waitstaff workingin outdoor patio areas where smoking is allowed could average 1.6 to 9.8 μg/m3 peryear. It is thus plausible that occupational exposure to PM2.5 in outdoor worksettings where smoking is allowed could exceed the Australian National EnvironmentProtection Measure for Ambient Air Quality benchmark annual average target of8μg/m3 .An increase of 5μg/m3 to 10 μg/m3 in average annual PM2.5 exposure is associated witha 3‐6% increase in all‐cause mortality.Personal monitoring studies have not yet been conducted to corroborate modelledestimates of staff exposure in these settings. Such studies should be conducted totest the modelled exposure estimates we have calculated.
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