Indoor concentrations of nicotine in low-income, multi-unit housing: associations with smoking behaviours and housing characteristics

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1 1 Department of Environmental Health, Harvard Shool of Publi Health, Boston, Massahusetts, USA; 2 Shool of Publi Health, University of California Berkeley, Berkeley, California, USA Correspondene to: Gary Adamkiewiz, Department of Environmental Health, Harvard Shool of Publi Health, Landmark Center West, 401 Park Drive, Boston, MA 02215, USA; gadamkie@hsph.harvard. edu Reeived 25 January 2009 Aepted 21 July 2009 Published Online First 13 August 2009 Indoor onentrations of niotine in low-inome, multi-unit housing: assoiations with smoking behaviours and housing harateristis T A Kraev, 1 G Adamkiewiz, 1 S K Hammond, 2 J D Spengler 1 ABSTRACT Objetive: An analysis of airborne niotine measurements olleted in 49 low-inome, multi-unit residenes aross the Greater Boston Area. Methods: Niotine onentrations were determined using passive monitors plaed in homes over a one-week sampling period and air exhange rates (AER) were sampled using the perfluoroarbon traer tehnique. Residents were surveyed through a questionnaire about smoking behaviour and a visual inspetion was onduted to ollet information on housing harateristis ontributing to seondhand smoke (SHS) exposure. Using a mass balane model to aount for the air exhange rate, volume of the home and sorption and re-emission of niotine on indoor surfaes, the effetive smoking rate (SR eff ) was determined for eah residene. Results: Niotine levels ranged from the limit of detetion to mg/m 3, with a mean of 2.20 mg/m 3 and median of 0.13 mg/m 3. Niotine measurements were signifiantly assoiated with the number of smokers in the household and the number of igarettes smoked in the home. The results of this study suggest that questionnaire reports an provide a valid estimate of residential exposure to tobao smoke. In addition, this study found evidene that tobao smoke ontamination in lowinome housing developments is not limited to homes with smokers (either residing in the home or visiting). The frequent report of tobao smoke odour oming from other apartments or hallways resulted in inreased levels of niotine onentrations and SR eff in non-smoking homes, suggestive of SHS infiltration from neighbouring units. Conlusion: These findings have important impliations for smoking regulations in multi-unit homes and highlight the need to redue involuntary exposure to tobao smoke among low-inome housing residents. Numerous epidemiologial studies have doumented the link between seondhand smoke (SHS) exposure and inreased morbidity and mortality. 1 Over the past two deades, authoritative reviews of the sientifi, engineering and medial literature have established a wide range of adverse health effets from SHS inluding ardiovasular disease, lung, breast and nasal sinus aner, asthma and other respiratory illnesses (partiularly in hildren), and low birth weight and sudden infant death syndrome (SIDS) in newborns. 1 4 Reent findings published by the US Surgeon General have determined that there is no safe level of exposure to seondhand smoke and even brief exposure an affet both hildren and adults. 1 Despite the inreased awareness of health impats and substantial progress in tobao ontrol, SHS remains a widespread and unavoidable health hazard for millions of hildren and non-smoking adults. Smoking in residential settings presents serious and substantial health hazards, as well as signifiant hallenges in proteting the health and wellbeing of residents. The home is the primary soure of SHS exposure for hildren, and along with the workplae, a predominant loation of exposure for adults. 1 It is estimated that 60% of hildren aged 3 11, or approximately 22 million hildren in the United States are exposed to SHS in their home. 1 Parental smoking aounts for almost 90% of the exposure in the home, followed by grandparents and other relatives that live in the residene. 5 For residents of multi-unit housing, the soure of this problem an extend beyond their residene. SHS an enter a smoke-free residene in a multi-unit housing omplex from shared air spaes, ventilation systems, windows, elevator shafts, hallways and holes in walls, pipes and eletri outlets. 6 In older buildings, about half to two-thirds of the air in a multi-unit residene an infiltrate from neighbouring apartments. 7 While eliminating smoking in indoor spaes protets non-smokers from SHS ontaminants, 8 other approahes suh as separating smokers from non-smokers, using air leaning devies or ventilation tehnology may redue, but does not eliminate exposure. 9 Few studies have investigated SHS exposure in low-inome, multi-unit housing; however, residents may be exposed to elevated levels owing to higher smoking rates and building fators suh as smaller units, poor ventilation and infiltration between units. 10 In addition, studies have shown that low-inome, and underserved raial/ethni minorities suffer disproportionately from tobaorelated morbidity and mortality, as well as inreased inidene of asthma, heart disease and aner The objetive of this study was to haraterise SHS exposure in low-inome housing developments in urban neighbourhoods surrounding Boston, Massahusetts. Speifially, we examined the distribution of airborne niotine onentrations as a marker of SHS and assessed the fators that ontribute to exposure in multi-resident housing. This study applied a mass balane model to examine the relation between indoor niotine onentrations, air exhange rates, home volume, and the sorption and re-emission of niotine on indoor surfaes. Using the resulting effetive smoking rates (SR eff ), we estimated the igarettes per day (igs/day) equivalene of SHS exposure in 438 Tobao Control 2009;18: doi: /t

2 eah home. We hypothesised that airflows within the building would be assoiated with elevated levels of SHS exposure. METHODS Study design This study is part of a omprehensive researh projet in ollaboration with the Harvard Shool of Publi Health (HSPH) and Dana Farber Caner Institute (DFCI) examining the soial and physial determinants of aner risk-related behaviours among multi-ethni residents in low-inome housing developments. As part of this projet, week-long integrated samples of vapour-phase niotine were olleted along with the smoking behaviour of residents. An ethnially diverse sample of residents from 49 units within four low-inome housing developments in the Greater Boston Area was randomly seleted to take part in the study. Partiipant eligibility inluded being between 18 and 64 years of age, speaking English, Haitian Creole or Spanish, and residing in a low-inome housing development in Cambridge, Somerville or Chelsea, Massahusetts. Residents were invited to partiipate in the study through meetings of the tenants assoiation, and through the distribution of posters and flyers at eah of the seleted housing developments. All researh protools were submitted for ethis review and approved by the institutional review board (IRB) at the Harvard Shool of Publi Health. Three methods were used to assess tobao smoke exposure. An interviewer-administered questionnaire defined household smoking behaviour. A visual inspetion observed evidene of smoking, while olleting information about potential housing harateristis ontributing to SHS levels in the home. Weeklong airborne niotine onentrations provided a diret measure of SHS. Air exhange rates were also determined over the same period as the niotine measurements. Field operations for this study were onduted between mid- Marh and mid-june The study required two home visits. During the first visit, a team of two trained researh assistants interviewed the resident, onduted a visual inspetion and set up the air sampling monitors. After six to seven days, the researh assistants returned for the seond home visit to retrieve the sampling equipment. Reords from the olletion instruments were sent to the HSPH laboratory for analysis. Questionnaire A questionnaire was used to obtain information in all 49 residenes sampled. Survey questions were derived from the HSPH Healthy Publi Housing Initiative (HPHI) 15 and a review of relevant published literature on indoor air pollution among urban, minority and low-inome populations. The survey was translated into Haitian-Creole and Spanish for non-native English speakers and a translator was provided to ondut the interview when needed. Before eah interview, a projet summary was reviewed with eah prospetive partiipant and a signed onsent form was olleted. The questionnaire assessed demographi information, residential history, household smoking behaviour and physial housing harateristis. Visual inspetion A visual inspetion observed signs of smoking suh as ative smoking, tobao odour and the presene of igarettes, igars, empty ashtrays, ashtrays with ashes, mathes or lighters. Other parameters reorded inluded housing disrepairs suh as holes or damage in the floors, walls and eilings, and unsealed pipe penetration. In addition, the number of rooms and volume of eah residene was measured. Analytial methods Passive air niotine monitors were used to measure vapourphase niotine emissions in eah residene. Passive diffusion monitors olleted vapour-phase niotine into a sodium bisulfate treated filter held in a 37-mm polystyrene assette. 16 Eah devie was plaed in the partiipants main living area (living room or family room) during the first home visit and remained in the residene for six to seven days. In the laboratory niotine was extrated from the filter, desorbed in water and analysed by gas hromatography. 16 Field blanks and dupliates were obtained for 5% of the samples. The limit of detetion (LOD), based on three times the mean blank values, was alulated at mg/m 3. All niotine monitors were analysed at the University of California, Berkeley. The perfluoroarbon (PFT) tehnique was used to measure air exhange rates in eah residene. 17 A non-toxi traer gas (perfluoromethyl ylohexane) released at a onstant rate, is sampled by diffusion onto an adsorbent in apillary absorption tubes (CAT). The soure was plaed in the middle of the main living area and the CAT was taped to the opposing wall a distane of six feet away from the soure. The PFT was thermally desorbed and quantified by gas hromatography with an eletron ion detetor. Assuming a well-mixed interior spae, air exhange rates are alulated based on a mass balane tehnique outlined by Dietz et al 17 at the Harvard Shool of Publi Health. Field blanks were olleted for 5% of all samples. Data analysis methods Data were maintained in ACCESS and analysed using Statistial Analysis Software version The Kruskal-Wallis one-way analysis of variane (ANOVA) was used to test for differenes in group means and exposure measures. Median onentrations were ompared aross different smoking behaviours and housing harateristis, and Wiloxon rank sum tests were performed to determine statistial signifiane at a p value of Mass balane model The effetive smoking rate (SR eff ) was alulated in order to better interpret variability of niotine onentrations in the residential environment. The SR eff aounts for the soure strength of the pollutant in eah residene based on the niotine onentration, air exhange rate (AER), volume of the home, and interation of niotine on indoor surfaes, suh as the gains and losses through sorption and desorption. This method relies on the omputation of the mass balane model (equation 1, where SR eff is the indoor effetive smoking rate (igarettes/day), Cin is the indoor niotine onentration (mg/m 3 ), R is the measured air exhange rate (h 21 ), V is the volume of the home (m 3 ), and EREF is the exposure relevant emission fator (mg/ igarette). Values of Cin, R and V were measured in eah home. Equation 1: Effetive smoking rate (SR eff ) The mass balane model from Sax et al 19 is rearranged to estimate the effetive smoking rate (SReff) in eah residene through the use of exposure relevant emission fators (EREFs). The EREF aounts for the sorptive uptake and re-emission of Tobao Control 2009;18: doi: /t

3 SHS onstituents representative of smoking rates, ventilation and furnishings in typial residential settings. The use of EREFs are more appropriate to real world senarios and provide an improved approah to estimating SHS exposure. 20 The EREFs for this exposure model were alulated using the measured values from Singer et al, 21 for niotine in a fully furnished room at three ventilation rates (low, moderate and high) representing values in typial residenes: 0.3 h 21 (396 (29) mg/ig), 0.6 h 21 (689 (50) mg/ig), and 2 h 21 (1270 (110) mg/ig). Using these data, a linear regression of EREF versus log-transformed AERs was used to estimate EREFs aross this range. For AERs below 0.2 h 21, an EREF of mg/ig was used, based on the predited estimate using this regression model. RESULTS Demographis Subjet demographis are summarised in table 1 and ompared between non-smoking and smoking partiipants. The study population was predominantly female (96%) with a mean age of 42.5 years (range 26 68). Of the 49 subjets enrolled in the study, 41% were white, 31% were Afrian Amerian, 26% were other rae/ethniity and 2% were Asian; 26% of the study population was of Hispani or Latino deent. Partiipants reported spending the majority of time over a typially 24-hour period in their residene, on average 14.2 hours at home, 2.8 hours at work, 2.2 hours shopping and doing errands, 1.9 hours at other loations, 1.8 hours at someone else s home and 1.1 hours ommuting. In addition, respondents reported that a member of the household was home during the day in 65% of the residenes. The demographi harateristis of smoking and non-smoking partiipants did not differ with respet to gender, age or household size. However, the smoking population was predominately white (73%), while the nonsmoking population was predominately raial/ethni minorities. Niotine onentrations Detetable levels of niotine were measured in 45 (94%) of the 49 residenes. Overall, niotine onentrations ranged from below the limit of detetion (LOD) mg/m 3 to maximum levels of mg/m 3. The mean niotine onentration of the study sample was 2.20 mg/m 3 and the median onentration was 0.13 mg/m 3. Table 2 presents the summary statistis of the niotine measurements by the smoking harateristis of the study population. Niotine onentrations were highly assoiated with partiipant smoking status (that is, whether subjets selfidentified as smokers or non-smokers) (p,0.0001). Of the subjets enrolled in the study, 69% (n = 33) were non-smoking partiipants and 31% (n = 15) were smoking partiipants. The smoking partiipants smoked an average of 12.5 igarettes per day (ranging from 2 30). Non-smoking partiipants had a median onentration of 0.06 mg/m 3 ranging from, LOD to 1.81 mg/m 3, while smoking partiipants had a median onentration of 2.93 mg/m 3 ranging from 0.09 to mg/m 3. The impat of household smoking status (that is, whether there were any smokers, inluding the study partiipant, living in the household) was signifiantly assoiated with niotine levels (p,0.0001). The number of household smokers living in Table 1 Population demographis of partiipants in four low-inome housing developments All partiipants Non-smoking partiipants Smoking partiipants Charateristis (n = 49) % (range) (n = 34) % (range) (n = 15) % (range) Mean age 42.5 (26 68) 43.0 (26 68) 41.3 (29 65) Mean household size 3.0 (1 7) 2.8 (1 6) 3.6 (1 7) Mean No of adults that live in residene 1.5 (1 3) 1.5 (1 3) 1.5 (1 3) Mean No of hildren under 18 that live in residene 1.6 (0 4) 1.3 (0 4) 2.1 (0 4) Number of residenes with hildren under % % % Gender Female 47 96% 32 94% % Male 2 4% 2 6% 0 0% Rae White 20 41% 9 27% 11 73% Afrian Amerian 15 31% 14 41% 1 7% Asian 1 2% 1 3% 0 0% Other 13 26% 10 29% 3 20% Ethniity Hispani 13 26% 9 27% 4 27% Non-Hispani 36 74% 25 73% 11 73% Language English primary language 27 55% 13 38% 14 93% Other 22 45% 21 62% 1 7% Questionnaire translation English 32 65% 17 50% % Haitian 11 22% 11 32% 0 0% Spanish 6 13% 6 18% 0 0% Plae of birth United States 25 51% 11 32% 14 93% Other 24 49% 23 68% 1 7% Duration of exposure Household member is home during the day % % % Mean years lived in residene 6.2 (,1 22) 6.8 (,1 22) 4.9 (,1 12) Mean years lived in development 8.7 (,1 33) 8.4 (,1 22) 9.3 (,1 33) 440 Tobao Control 2009;18: doi: /t

4 Table 2 Summary statistis of niotine onentrations by smoking behaviour Smoking behaviour Niotine (mg/m 3 ) (n = 48)* (%) Median Mean Minimum Maximum SE p Value Partiipant smoking status: Non-smokers 33 (69) ,LOD Smokers 15 (31) , Number of smokers in household: No response{ 7 (15) ,LOD (48) ,LOD (22) (15) , Visitors smoke in home: No 32 (67) ,LOD Yes 16 (33) , Smoking soure: No response{ 7 (15) ,LOD None 21 (44) ,LOD Visitors only 2 (4) Residents only 5 (10) Resident and visitor smoking 13 (27) , Number of igarettes smoked in home: No response{ 18 (38) ,LOD igs/day 14 (30) igs/day 5 (10) igs/day 5 (10) igs/day 2 (4) >20 igs/day (a pak or more) 4 (8) , Home lassifiation: Non-smoking homes{ 19 (46) ,LOD Smoking homes" 22 (54) ,LOD , *One passive niotine sample was subjet to equipment problems and was exluded from the analysis. {Data not available for entire ohort. {Smoke-free homes where neither household members nor visitors smoked in the residene. "Homes with one or more smokers in the household, and/or smoking visitors. Inludes data from smoke-free homes where signs of smoking (that is, ative smoking, visible igarettes, igars, ashtrays with ashes, mathes or lighters, and/or smoking odour) were observed during the visual inspetion. the home ranged from none to two, with 48% (n = 23) of the residenes having no smokers living in the home, 22% (n = 11) having one smoker and 15% (n = 7) having two smokers. As antiipated, niotine measurements inreased with the number of smokers in the home; households with none, one and two smokers had a median onentration of 0.06 mg/m 3, 1.81 mg/m 3 and 3.13 mg/m 3, respetively. Visitor smoking status (that is, whether non-residents, suh as relatives, friends, neighbours or babysitters ever smoked in the home) was signifiantly orrelated with niotine measurements Figure 1 Cumulative distribution of effetive smoking rates (SR eff )by smoking status. a Data not available for entire ohort. (p,0.0001). While 33% of the subjets (n = 16) reported permitting visitor smoking in the home, 67% (n = 32) restrited visitor smoking. Homes with no-smoking visitors had a median onentration of 0.07 mg/m 3 (n = 32), while homes with smoking visitors had a median onentration of 2.17 mg/m 3 (n = 16). The soure of smoking (that is, visitor smoking only, resident smoking only and resident and visitor smoking) signifiantly influened the niotine levels in the home (p,0.0001). Smoking in the home was reported as oming from 4% visitors only, 10% residents only and 27% both residents and visitors, with median Tobao Control 2009;18: doi: /t

5 onentrations inreasing from 0.18 mg/m 3, 0.69 mg/m 3 and 2.93 mg/m 3, respetively. The number of igarettes smoked per day in eah residene was signifiantly orrelated with niotine levels (p,0.0001). Daily exposure to igarette smoke in the home was reported by 32% of the study population. The number of igarettes smoked in the home on a typial day ranged from none (30%), 1 5 igarettes (10%), 6 10 igarettes (10%), igarettes (4%), to a pak or more igarettes per day (8%). Households reporting 0 igarettes smoked per day had a median niotine level of 0.11 mg/m 3, ranging from mg/m 3, while households with 1 5, 6 10 and igarettes smoked per day had inreasing median onentrations of 1.19 mg/m 3, 1.81 mg/m 3 and 9.28 mg/m 3, respetively. The median onentrations were highest when partiipants smoked a pak or more igarettes per day (15.74 mg/m 3 ), suggesting that the household smoking rate is a primary determinant of indoor onentrations. SHS exposure in non-smoking and smoking homes In order to ompare SHS exposure in non-smoking homes with those in smoking homes, data from two subgroups were ompiled. Non-smoking partiipants who lived in smoke-free homes where neither household members nor visitors smoked in the residene were lassified as non-smoking homes (NSH). All other residenes were onsidered smoking homes (SH), defined by one or more smokers in the household, and/or smoking visitors. Another indiator of smoking homes was whether signs of smoking were observed during the visual inspetion suh as ative smoking, visible igarettes, igars, empty ashtrays with ashes, mathes or lighters and/or smoking odour. This method was effetive in revealing mislassifiation of home environments as non-smoking homes when notieable signs were evident. Inongruity between questionnaire reported smoke-free homes and observed tobao use was deteted in two residenes. Signs of smoking were also an effetive preditor of SHS exposure (p,0.0001). Homes in whih no signs were observed had a median niotine onentration of 0.06 mg/m 3, while homes in whih one or more signs of smoking were present had a median of 2.53 mg/m 3. Niotine was deteted in 89% (17/19) of non-smoking homes and 95% (21/22) of smoking homes. (It should be noted that the one smoking home where niotine was not deteted was lassified as a smoking home due solely to visual signs of smoking in the home. No smoking ativity by residents or visitors was reported in this home, and thus, it ould have been assigned as a non-smoking home. If this home were re-lassified, 100% of smoking homes showed detetable levels of niotine.) Air niotine levels in non-smoking homes were low, ranging from the LOD to 0.28 mg/m 3, with a median of 0.04 mg/m 3 and mean of 0.08 mg/m 3. Conentrations were signifiantly higher in smoking homes, ranging from the LOD to mg/m 3, with a median of 1.50 mg/m 3 and a mean of 4.66 mg/m 3 (p,0.0001). Using the mass balane model, the residene speifi effetive smoking rate (SR eff ) was alulated for eah residene. Figure 1 presents the umulative distribution for SR eff by smoking status. Smoking homes had a range of igs/day, with a median of 3.88 igs/day and a mean of igs/day (p,0.0001). Homes where two residents smoked, and homes where both residents and visitors smoked were among the highest SR eff. However, SHS ontamination, as measured by airborne niotine levels, was not limited to smoking homes. Conentrations in non-smoking homes were equivalent to a range of igs/day, with a median value of 0.15 igs/day and a mean of 0.25 igs/day. The SR eff aross non-smoking homes shows that household smoking restritions do not guarantee a smoke-free residene. Surprisingly, some nonsmoking homes were exposed to the equivalent of approximately one igarette per day smoked in their home. Potential infiltration of SHS in residenes The soure of SHS exposure in non-smoking homes was further explored by determining the residents pereption of SHS infiltration from hallways and neighbouring units. Partiipants were ategorised into two groups, those who deteted tobao smoke odour transfer frequently (that is, a few times per week or everyday) and those who deteted tobao smoke odour infrequently (that is, less than one per year, a few times a year, or a few times per month). Table 3 illustrates the trend in whih the frequent report of tobao smoke odour oming from other apartments or hallways resulted in inreased levels of niotine onentrations and SR eff in non-smoking homes. Residents of non-smoking homes who reported frequent tobao smoke odour were exposed to higher median niotine onentrations (0.06 mg/m 3 ) than those who rarely smelled igarette smoke (0.04 mg/m 3 ), although the p value Table 3 Tobao smoke odour from other apartments and hallways. Comparison of infrequent vs frequent tobao smoke odour deteted{ Tobao smoke odours from other apartments or hallways Niotine (mg/m 3 ) SR eff (ig/day) Smoking status Tobao smoke odour deteted{ No Median Mean p Value No Median Mean p Value All partiipants Infrequent Frequent Non-smoking partiipants Infrequent Frequent Smoking partiipants Infrequent Frequent Non-smoking homes Infrequent Frequent Smoking homes Infrequent Frequent {Response from question, In your apartment, how often do you smell igarette odour from other apartments or the hallways? {Infrequent = (( one/year, few/year, few/month), frequent = (few/week, every day). 442 Tobao Control 2009;18: doi: /t

6 was not statistially signifiant. The effetive smoking rates further onfirmed these relations, as those reporting frequent odour detetion (0.20 igs/day) were higher than those reporting infrequent odour detetion (0.14 igs/day), although the p value of was not statistially signifiant. Surprisingly, smoking partiipants and smoking homes had an inverse trend. This result may be attributed to the smoking partiipants inability to identify an external soure of tobao smoke odour as well as the non-smoking partiipants. In addition, smoking homes had a higher mean AER of 0.50 h 21 and median 0.37 h 21 ranging from 0 to 1.45 ompared to non-smoking homes with a mean of 0.39 h 21, median of 0.26 h 21, ranging from 0 to 0.99 h 21 (p = 0.357). DISCUSSION The purpose of this study was to determine residential exposure to SHS in low-inome, multi-unit residenes aross the Greater Boston area. The results of this study were onsistent with previous researh that measured niotine onentrations in residential environments using similar methods. Median niotine levels between 1 mg/m 3 and 3 mg/m 3 and ranging from 0.1 mg/m 3 to 8 mg/m 3 were reported in homes of smokers aross the United States in several studies Although the median niotine level for smoking homes (2.17 mg/m 3 ) in this study was omparable to previous studies, the range was notably higher, with measurements up to mg/m 3. Reported inreases in niotine yield in reent years may partially explain differenes between this study and earlier reports. For example, several reent analyses of niotine yield from major brand name igarettes sold in Massahusetts from 1997 to 2005 found that manufaturers have steadily inreased the levels of niotine in igarettes by 11% over this period. Despite this trend, differenes in ohort demographis between studies are likely the dominant soure of variability. For example, a study of 291 ethnially diverse low-inome families in New England measured elevated niotine onentrations (reahing 18 mg/m 3 ), muh higher than previous studies assessing exposure in middle-inome and upper-inome families. 28 This study examined niotine levels in relation to household smoking behaviour and assessed the variability of exposure by smoking status. While the prevalene of smoking was high in our ohort (31%), this rate is onsistent with reported rates among low-inome populations in Boston (34.4%). 29 Partiipant, household, and visitor smoking status were found to be highly preditive of measured niotine onentrations. In addition, vapour phase niotine measurements were highly orrelated with the number of igarettes reported being smoked in the home per day. Previous studies on the validity of questionnaire reported smoking have also found assoiations with air niotine onentrations and partiipant reports of smoking in the home The results of this study indiate that the essation of home smoking will signifiantly redue SHS ontamination and exposure. This study found evidene to suggest that SHS ontamination is not limited to homes with ative smokers. SHS may infiltrate into homes through windows, doors, shared air spaes, holes and ventilation systems if igarettes are smoked outside or in neighbouring residenes. Little is known about the variability of SHS when ontamination is generated by smokers from outside the building envelope or from adjoining units. However, this study points to an observed assoiation between elevated niotine onentrations and effetive smoking rates and the inreased frequeny of smelling igarette odour from other apartments, hallways or outside the building. These findings suggest that living in a multi-unit dwelling with smoking residents in the building may plae non-smokers at risk of SHS exposure. These findings impliate that reduing outside soures of igarette smoke is an effetive strategy for lessening household exposure levels. The use of the questionnaire to evaluate the respondents exposure to SHS presented limitations that should be onsidered. Mislassifiation of exposure may result from the respondents lak of awareness of igarette exposure, inadequate reall, or possible deeption in reporting smoking status. However, the visual inspetion tool, when used in onjuntion with a questionnaire, was helpful to validate the smoking information provided by the respondents. In addition, this study did not ontrol for the loation of smoking in the residene in relation to the sampling area. Additional information on the smoking loale (that is, kithen, bedroom, patio, et) may improve the observed relation between niotine levels and the soure strength in the home. More researh is needed to determine whether SHS exposure is best haraterised by the niotine level in the main living area, bedroom, highest level in the home or an average of all of the rooms. 33 Reent studies have also highlighted the potential for deposited or adsorbed partiulates or gases to ontribute to household exposure to toxi ompounds originating from smoking ( thirdhand smoke exposure ). 34 Owing to the ompliated behaviour of many semivolatile ompounds, inluding niotine, in indoor environments, 35 it will be ritial to develop mehanisti models to orretly identify dominant exposure pathways and estimate health risks from these exposures. Although poliy efforts ontinue to address appropriate boundaries of smoking in the publi and private setor, restrition of smoking in multi-unit homes has not reeived the same degree of attention. Publi health poliies to limit SHS exposure in publi spaes and enourage the elimination of smoking in the home are ritial. Sine ontaminated indoor environments may present health risks to unsuspeting nonsmokers, regulations may need to require the dislosure of the smoking status of previous tenants and neighbouring apartments. Approahes for addressing the issue of smoke infiltration in low-inome housing inlude eduating landlords and property managers to implement voluntary smoke-free poliies, reating rules to restrit smoking in ommon spaes suh as entranes, elevators and laundry rooms within the housing omplex and hanging building design and operation to ontrol infiltration of ontaminated air. 36 Loal health jurisditions an work with owners and managers of multi-unit residenes to enourage the designation of smoke-free buildings for the health as well as enjoyment of the residents. In addition to poliy restritions on smoking, efforts to eduate the publi about the risks assoiated with SHS exposure at home may be an effetive means of reduing exposure. Healthare providers and publi health advoates need to play a stronger part in informing the publi about the health effets of SHS exposure, and the positive impat that smoking restritions an have on household members. Interventions to motivate smokers to onsider essation through the awareness of the benefits of exposure redution should be implemented in lowinome housing developments. Given the relatively serious health onsequenes assoiated with exposure to SHS, this study highlights the importane of ontinued efforts to develop and evaluate effetive exposure assessments targeting raial/ ethni minorities and low-inome housing populations. Suh efforts would provide muh needed information and eduation about this very ommon publi health problem and give Tobao Control 2009;18: doi: /t

7 What this paper adds Limited researh has investigated seondhand smoke (SHS) exposure in low-inome, multi-unit housing; however, residents may be exposed to elevated levels of SHS beause of higher smoking rates and building fators suh as smaller units, poor ventilation and infiltration between units. This study examines the relation between indoor niotine onentrations, air exhange rates, home volume and sorption and re-emission of niotine on indoor surfaes, in order to determine the prevalene of SHS exposure in low-inome, multi-unit residenes. The results of this analysis indiate that SHS is not limited to residenes with smokers (either residing in the home or visiting). The frequent report of tobao smoke odour oming from other apartments or hallways resulted in inreased levels of niotine onentrations in non-smoking homes, suggestive of SHS infiltration from neighbouring units. The study also demonstrates that effetive smoking rates may be an important and valid measure that an be used to improve our understanding of the variability of niotine onentrations in the residential environment. These findings have important impliations for smoking regulations in multi-unit homes and highlight the need to redue involuntary exposure to tobao smoke among lowinome housing residents. residents of multi-unit homes the tools to protet their families from the detrimental health effets of seondhand smoke. Aknowledgements: The authors would like to aknowledge the administrative and field staff at the Harvard Shool of Publi Health, Dana Farber Caner Institute and the Harvard Extension Shool, and the study partiipants for their ontributions to this projet. They also thank Beatriz Vinas and Jose Vallarino at the Harvard Shool of Publi Health, Brett Singer at the Lawrene Berkeley National Laboratory and Amy Harley, Lorraine Wallae, Marty Alvarez-Reeves, Ruth Lederman, Mike Massagli, Anne Stoddard, Roberta Goldman and Glorian Sorensen (PI) at the Dana Farber Caner Institute for their ontributions to the overall study design and implementation. Funding: This researh was supported by the Harvard Shool of Publi Health and Dana Farber Caner Institute, with funding provided by the National Caner Institute, (grant No 1 R01 CA A1). Prinipal investigator: Glorian Sorensen. Competing interests: None. Attributable departments/institutions: Department of Environmental Health, Harvard Shool of Publi Health, Landmark Center West, 401 Park Drive, Boston, MA 02215, USA. Provenane and peer review: Not ommissioned; externally peer reviewed. REFERENCES 1. US Department of Health and Human Servies. 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