ASSESSMENT OF AIR-QUALITY IN STOCKHOLM BY PERSONAL MONITORING OF NONSMOKERS FOR RESPIRABLE SUSPENDED PARTICLES AND ENVIRONMENTAL TOBACCO-SMOKE

Exposure to respirable suspended particles (RSP) from all sources and environmental tobacco smoke (ETS) was assessed for 190 nonsmokers in S tockholm during 1994. Each subject wore a personal monitor for 24-h, p rovided saliva samples for cotinine analysis, and completed a detailed questionnaire about air quality and life-style. The subjects consiste d of housewives and househusbands in one main group and working men an d women in the second. The housewives and househusbands wore a single monitor throughout the 24-h period and the working subjects wore one m onitor at work and a separate monitor while not at work. The geodemogr aphic distribution of the recruited subjects accurately reflected the population of Stockholm. For most of the subjects, exposure to ETS and nicotine was at or below the limits of quantification (LOQ). This fin ding was supported by the fact that about 80% of the recruited subject s claimed that their exposure to ETS was ''none'' or ''low.'' The conc entration of RSP was found to be highest (median 39 mu g . m(-3)) in h omes where smoking occurred and below the LOQ in the workplace irrespe ctive of its smoking status. These levels are at the lowest end of typ ical indoor air levels for RSP. For the housewives and househusbands l iving in smoking homes (nonsmoking homes in parentheses), the median e xposure levels were 39 mu g . m(-3) (18 mu g . m(-3)) for RSP, 17 mu g . m(-3) (0.12 mu g . m(-3)) for ETS particles, and 1.1 mu g . m(-3) ( 0.05 mu g . m(-3)) for nicotine. Both the pre- and postmonitoring coti nine saliva levels measured for these housewives and househusbands wer e 2.9 ng . ml(-1) (pre-0.56 ng . ml(-1), post- 0.41 ng . ml(-1)). The highest exposure levels were recorded for the housewives and househusb ands in the age range of 35-49 years. For the working subjects, the ex posure measured in smoking workplaces (nonsmoking workplaces in parent heses) gave median levels of 16 mu g . m(-3) (16 mu g . m(-3)) for RSP , 1.1 mu g . m(-3) (0.42 mu g . m(-3)) for ETS particles and 0.2 mu g . m(-3) (0.15 mu g . m(-3)) for nicotine. Similarly measured exposures at home (nonsmoking homes in parentheses), including all other locati ons outside the workplace, gave median levels of 24 mu g . m(-3) (19 m u g . m(-3)) for RSP, 1.4 mu g . m(-3) (0.2 mu g . m(-3)) for ETS part icles, and 0.15 mu g . m(-3) (0.07 mu g . m(-3)) for nicotine. Overall , the exposure levels of ETS due to living with smokers in Stockholm w as found to be much lower than similar exposures measured previously i n the United Kingdom and the United States. Over 70% of all the nicoti ne measurements and 60% of all the ETS measurements were below the LOQ . When the median values for nicotine and ETS particles are converted to cigarette equivalents, Stockholm housewives and househusbands livin g with smokers would receive 6-9 cigarette equivalents per year, worki ng nonsmokers living with smokers would receive 0.6-0.7 cigarette equi valents at home, and nonsmokers working with smokers would be exposed to 0.1-0.2 cigarette equivalents at work. The exposures were therefore up to six times greater at home than in workplaces where smoking was occurring. Although all the subjects were recruited as nonsmokers on t he basis of their self-reported nonsmoking status, saliva cotinine mea surements were used for confirmation. Subjects with cotinine levels be low 25 ng . ml(-1) were considered to be nonsmokers although the selec tion of a threshold level within the range of 10-50 ng . ml(-1) was no t considered to be critical. With a threshold of 25 ng . ml(-1), betwe en 2.7% and 5.3% were later shown to be misclassified as nonsmokers, d epending on the definition of misclassification used. During the study period the air quality in Stockholm could be described according to B ritish nomenclature as ''very good'' for the majority of the time. The daily average at no time fell below ''good,'' and the maximum hourly nitrogen dioxide level was 111 mu g . m(-3) (inner city at street leve l) on the coldest day (average -0.2 degrees C).