polychlorinated biphenyls 
 ( pcbs ) are a ubiquitous group of persistent 
 organic pollutants that are carcinogenic and neurotoxic , with potential 
 endocrine disrupting and immune - suppressing activity . toxicological studies demonstrating the dioxin - like properties of 
 pcbs , and industrial accidents in japan 
 and taiwan led to bans on the commercial 
 production and sale of pcb mixtures in many countries . despite these 
 actions , pcbs are a persistent public health threat in indoor environments , 
 because they were purposefully added to household sealants , paint 
 plasticizers , wood finishes , flame retardants , light ballasts , and 
 electrical capacitors in appliances . pcbs are present 
 in modern pigments used in household paint and many consumer products . non - aroclors  , 
 because they are unrelated to the commercial mixtures banned from 
 production in the 1970s . pcbs are also present in outdoor environments 
 due to contributions from legacy , industrial sites ( e.g. , ref ( 12 ) ) , diffuse , contemporary 
 urban sources , and , to a lesser amount , volatilization 
 from soil and water bodies . pcbs are highly lipophilic ; 
 bioaccumulate in fats , lipids , and 
 waxes ; bioconcentrate in food chains ; and are semivolatile . they are 
 both present in the gas phase and associated with solids at ambient 
 temperatures . because of high pcb concentrations in some animals , 
 studies of dietary pcb exposure have historically taken precedence 
 over dermal and inhalation exposure . however , airborne emissions from 
 newly produced pcbs and legacy sources may lead to inhalation exposure 
 at levels comparable to , and sometimes higher than , dietary exposure . there is also rising evidence that many lower - mw congeners are mutagenic 
 and tumor promoting ( pcb 3 , 15 , 52 , 77 ) endocrine 
 disrupting , and more strongly agonistic 
 toward thyroid receptors . inhalation exposure has been estimated on a limited 
 basis for residential , school , and other public environments , via 
 indoor air and sera pcb concentrations ( e.g. , 
 ref ( 21 ) ) , but these 
 estimates are lacking for north american urban environments . non - north american estimates are often limited 
 to world health organization ( who ) indicator congeners ( pcb 28 , 52 , 
 101 , 138 , 153 , 180 ) and dioxin - like pcbs . all mono- and dichlorinated 
 congeners , and some other abundant congeners ( e.g. , pcb 99 ) have been 
 excluded from these prior estimates , despite their greater likelihood 
 of occurring in the gas phase . here we estimate inhalation exposure 
 in urban and rural environments 
 for 201 pcb congeners represented in 156 chromatographic peaks via 
 indoor and outdoor air concentrations at schools and homes . we also 
 estimate dietary exposure to 40 pcb congeners using the most comprehensive 
 market basket survey for pcbs in north america and national health and nutrition examination survey ( nhanes ) 
 food ingestion rates . this congener - specific 
 approach , and the breadth of sampling performed under the aesop study 
 ( airborne exposure to semi - volatile organic pollutants ) , allow an 
 expansive view of pcb exposure for urban and rural cohorts in east 
 chicago , indiana ( ec ) and the region in and around columbus junction , 
 iowa ( cj ) . with these data , we aim to determine : ( 1 ) the congener - specific 
 and pcb inhalation and dietary exposure rates for individuals 
 in both locales ; ( 2 ) the relative importance of school , home , and 
 outdoor environments to inhalation exposure ; and ( 3 ) the role of generational 
 and gender differences on exposure . we hypothesize that individuals 
 in ec will have greater inhalation exposure than individuals in cj , 
 because of the proximity of ec homes to the chicago airshed and the 
 heavily contaminated indiana harbor and ship canal ( ihsc ) . all inhalation exposure data are 
 derived from the aesop study ( figure 1 ) , the 
 purpose of which is to evaluate population - level exposure to pcbs 
 in urban ( ec ) and rural ( cj ) cohorts . the region surrounding cj has 
 no known significant pcb sources and a population of less than 5000 
 individuals . in contrast , ec is an impoverished community in the greater 
 chicago metropolitan area whose industrial sites , including refineries , 
 steel mills , and the ihsc , have created potentially strong sources 
 of pcbs . cohorts of 120 mothers and 138 children who breathe air from these 
 environments have been recruited to the aesop study through middle 
 schools . prior to enrollment , subjects provided informed consent or 
 assent in either english or spanish . all aspects of the aesop study 
 have been approved by the institutional review board at the university 
 of iowa . air sampling at participants homes and schools has 
 occurred on a quarterly ( homes ) and bi - quarterly ( schools ) basis ( i.e. , 
 45 days ) . demographic , activity , occupational , and dietary questionnaires 
 have been administered in english or spanish on a yearly basis by 
 bilingual , trained field interviewers . the sampling and analysis scheme 
 for the study is illustrated in figure 1 . analysis 
 of saliva and blood serum samples , although not addressed herein , 
 provides complementary data sets discussed elsewhere . sampling and analysis scheme for aesop study . artist : jeanne dewall . 
 air sampling , questionnaires , subject enrollment , and gc - ms / ms analysis 
 are described in this paper . collection and analysis of saliva and 
 blood complete the aesop study data set , but are described elsewhere . we used passive air samplers ( pas ) 
 to measure pcb concentrations indoors and outdoors at schools and 
 homes . pas collect pcbs on polyurethane foam disks ( puf ) from gas 
 and particulate phases , at a rate dependent upon the molecular diffusivity 
 of airborne species , chemical phase equilibria , and deposition kinetics . we determined the effective sampling rates for our pas using a mass 
 transfer model that predicts uptake of pcbs by advection and diffusion 
 as a function of meteorological parameters . it improves upon the use of 
 depuration compounds to determine sampling rate , by incorporating spatial- , temporal- , and congener - specific 
 data , and thereby increases accuracy in exposure calculations . the resulting sampling rates generally increased with molecular weight , 
 varying from 2.5 md ( pcb 4 ) to 3.4 
 md ( pcb 205 ) for indoor environments 
 and from 4.1 md ( pcb 4 ) to 7.3 md for outdoor environments ( pcb 169 ) . sampling rates are roughly 2-fold greater for outdoor samples than 
 for indoor samples , due to higher wind speeds and advective mass transfer 
 outdoors . prior 
 to deployment , puf were cleaned ( 24 h , soxhlet apparatus ) with a 1:1 
 ( v / v ) hexane / acetone mixture and wrapped in aluminum foil within ziplok 
 bags for storage and transport . those pufs ready for deployment were 
 installed in pas housing and subsequently retrieved by trained field 
 staff . resulting puf samples were spiked with surrogate standards 
 ( 50 ng each of pcb 14 , deuterated-65 , and 166 ) , extracted with the 
 same hexane / acetone mixture ( accelerated solvent extractor , dionex 
 ase-300 ) , cleaned through a column of silicic acid , and concentrated , 
 as described by persoon and hornbuckle . laboratory blanks and field blanks were included at a 10% rate and 
 treated the same as samples . finally , after addition of internal standards 
 ( 20 ng each of deuterated - pcb 30 and 204 ) , samples were analyzed by 
 gas chromatography with tandem mass spectrometry ( gc - ms / ms , agilent 
 6890n quattro micro gc , waters micromass ms technologies ) in multiple 
 reaction monitoring mode , using a method derived from epa method 1668c , 
 but substantially modified for analysis with the aforementioned instruments . transition ions were selected for each homologue 
 group allowing greater separation of congeners from each other and 
 from background noise than possible using electron capture detection . we used a 60 m supelco spb - octyl capillary column for chromatographic 
 separation to isolate most of the dioxin - like congeners . we were able 
 to quantify 201 congeners as a set of 156 individual or coeluting 
 chromatographic peaks . further details of this method are described 
 elsewhere ( supporting information ( si ) ) . deuterated standards were obtained from cdn isotopes ( quebec , canada ) , 
 and nondeuterated standards from accustandard ( new haven , usa ) . recoveries 
 of surrogate standards ( arithmetic mean  se ) averaged 83  
 2% ( pcb 14 ) , 92  2% ( deuterated - pcb 65 ) , and 87  2% ( pcb 
 166 ) . congener - specific limits of quantification ( loqs ) were calculated 
 as the 95% confidence interval   of the 
 field blank mass per sample . most 
 of the congener loqs were below 0.05 ng ( supporting 
 information ( si ) , table s1 ) . infrequently detected congeners 
 pcb 23 ( loq = 0.014 ng sample ) , 126 ( 0.0047 ng 
 sample ) , 159 ( 1.0 ng sample ) , and 209 ( 0.050 ng sample ) had loqs higher 
 than many sample concentrations , and were disregarded in exposure 
 assessments and other analyses presented here - in . inhalation exposure for each subject 
 was estimated as the time - integrated product of their airborne pcb 
 congener concentrations and subject - specific inhalation rates : eq 1ti is 
 time spent in location i ( hr d ) ; q is the calculated 
 weight- , gender- , and age - specific inhalation rate ( md ) ; [ pcb]j is the airborne concentration of the jth pcb congener ( ng m ) ; and f is a conversion factor , 1.52  10 g 
 ngd hr yr . the time ( ti ) and inhalation rate ( q ) terms 
 were derived from questionnaire data , while [ pcbj ] was derived from pcb measurements . seasonal activity data 
 ( ti ) was matched with 
 corresponding seasonal pcb concentrations , but significant seasonal 
 differences were only observed for indoor ec home samples ( summer 
 vs nonsummer ) ( p=0.009 ) . modeled locations include ( i = 1 ) inside homes , ( i = 2 ) inside schools , ( i = 3 ) outdoors , and ( i = 4 ) all other 
 environments ( e.g. , workplace ) . inhalation exposure at home 
 is derived from pas measurements at each subject s household 
 ( typically two indoor samples ) , whereas inhalation exposure outdoors 
 and at schools is estimated from mean concentrations at each locale 
 ( outdoors : cj n = 41 , ec n = 48 ; 
 schools : cj n = 11 , ec n = 13 ) . 
 inhaled concentrations in other environments ( i = 
 4 ) ( e.g. , offices , stores , churches ) are imputed using mean indoor 
 home concentrations in the respective locales as a proxy ( cj n = 35 , ec n = 34 ) . dietary exposure to pcbs was calculated 
 as the product of u.s . average food consumption rates ( nhanes , 26 ) 
 and pcb concentrations in fish , dairy , meat , oils , and eggs ( canadian 
 total diet survey ( tds ) , health canada ) . age- and gender - specific nhanes food ingestion rates were used , 
 creating differences between subgroups dietary exposure . this 
 tds includes 40 abundant pcb congeners and is the most comprehensive 
 dietary data set in north america . data from toronto ( collected in 
 1996 ) and winnipeg ( 1994 ) were used as the geographically closest 
 proxies to ec and cj , respectively . however , winnipeg was chosen as a proxy 
 for cj because of its geographical context ( i.e. , great plains rather 
 than great lakes ) and more agriculture - based economy relative to toronto . oil , margarine , butter , and poultry data were unavailable for winnipeg , 
 and a 10-year national tds average was used as a substitute for these 
 food groups . the acquisition , extraction , clean up , analysis 
 and qa / qc measures for the canadian tds samples are as described in 
 newsome et al . tds foods were collected from supermarkets , 
 prepared as for consumption , composited into categories , and quantified 
 by gc / ms . here 
 we use congener- , location- , and food - specific concentrations from 
 the same data set , but which were previously unpublished in this form . student s t test ( two - sided , unequal variances ) was used to evaluate 
 statistical 
 differences between cohorts and air samples . all sample distributions 
 of home air measurements met assumptions of log - normality and were 
 analyzed after log transformation , whereas sample distributions of 
 school air measurements were normally distributed and were not log - transformed . a paired student s t test ( two - sided ) was 
 used to evaluate children s vs mothers exposure in 
 each locale . the use of grubbs test revealed four households 
 which had consistently high pcb concentrations . additional 
 samples from these households were quantified and validated these 
 extreme values , which were excluded from population estimates . cohorts for this paper were 
 selected from the pool of aesop study 
 participants on the basis of enrollment in the most recent study year 
 ( 20122013 ) , logical consistency of their activity data with 
 other questionnaire responses , deployment duration of corresponding 
 air samples ( i.e. , if within 90  14 days ) , and fulfillment of 
 quality assurance and quality control ( qa / qc ) criteria ( figure 2 ) . logical consistency included , for example , similarity 
 between a subject s work history ( e.g. , 40 h / week ) and their 
 activity data ( e.g. , > 40 h / week in  other  inhalation 
 category ) . the resulting ec cohort ( 33 households ) had lower incomes 
 ( p < 0.001 ) , poverty income ratios ( pir ) ( p = 0.001 ) , and years of education ( p = 
 0.01 ) than the cj cohort ( 35 households ) ( table 1 ) . hispanic individuals represent a large component of participants 
 in both locations ( 71% in ec and 53% in cj ) ( table 1 ) . however , differences in cohort demographics directly or indirectly 
 effect pcb concentrations described here - in . for example , income disparities 
 may help explain differences in pcb concentrations in ec v cj , because 
 the use , identification , and removal of pcbs requires economic decisions . we do not assess these possibilities here , but rather characterize 
 the cohort in a manner consistent with epidemiological norms . geometric mean ( se ) pcb 
 indoor air concentrations for ec homes ( 1.0 ( 0.02 ) ng m ) were significantly higher ( p < 0.001 ) than 
 geometric mean pcb indoor air concentrations for cj homes 
 ( 0.44 ( 0.1 ) ng m ) . one outlier home in ec had 
 pcb indoor air concentrations of 74  40 ng m ( n = 3 samples ) . three ( 3 ) outlier homes in cj , 
 had arithmetic mean pcb indoor air concentrations (  
 se ) ranging from 7.2  4.1 ng m to 17.3  
 1.7 ng m ( n = 3 ) . arithmetic 
 mean pcb indoor air concentration at ec schools ( 6.4  
 0.1 ng m , n = 13 ) was higher 
 than arithmetic mean pcb indoor air concentrations at ec homes 
 ( p = 0.013 ) , likewise for cj schools ( 8.4  
 0.4 ) ng m , n = 11 ) and homes 
 ( p < 0.001 ) . cj schools also appear to be enriched 
 in higher - mw congeners as compared to cj homes ( figure 3 ) . ec middle schools were built in 1968 and 1976 , while the 
 cj middle school was built in 1918 ( table 1 ) . outdoor samples in both locations had about 10-fold lower pcb 
 concentrations than was measured inside homes or schools , but congener 
 profiles were very similar inside and outside homes in the same locale 
 ( figure 3 ) . qa / qc criteria 
 include recovery of surrogate standards between 40 and 150% and concurrent 
 collection of field blanks . data 
 derived from census reports 
 for the surrounding community : east chicago , indiana and louisa county , 
 iowa ( united states census bureau ( uscb ) ( 2014 ) , state data center 
 of iowa statistics , available at http://www.iowadatacenter.org/ ) . data for columbus community 
 school 
 district ; population values are estimated from city census data plus 
 a percentage of the nonmunicipal louisa county population ( uscb 2014 ) . children s time spent in 
 schools , as used for exposure modeling , was determined by school calendars , 
 not questionnaires ( this table ) . sum (  ) pcb concentrations 
 in sampled foods range from below detection limits ( e.g. , skim milk ) 
 to 6.7 ng g wet weight ( i.e. , fresh marine fish 
 sampled in toronto ) . for both locales , fish had the highest pcb concentrations ( e.g. , cj : 4.5  
 1.3 ng g ) followed by eggs , lipids and oils ( 1.0 
  0.2 ) ng g ) , meat ( 0.55  0.03 ) ng 
 g ) and dairy ( 0.37  0.12 ) ng g ) . five hexa- and pentachlorinated congeners ( pcb 99 , 110 , 118 , 138 , 
 and 153 ) accounted for 42% and 49% of the pcbs measured in toronto , 
 and winnipeg foods , respectively . the remaining 35 pcbs were present 
 at concentrations of 375 pg g wet weight or less . for both locales , mean inhalation 
 exposure was greater for children than for mothers ( figure 4 ) ( p < 0.001 ) . this significant 
 difference is driven by greater airborne pcb concentrations 
 in schools than homes ( figure 3 ) , and the greater 
 amount of time that children spend in schools than do mothers ( table 2 ) . for aesop children , about half of pcb inhalation 
 exposure occurred inside schools , while mothers received about two - thirds 
 of their inhalation exposure inside homes . outdoor environments represented 
 < 5% of inhalation exposure ( figure 4 ) , due 
 to lower pcb concentrations and less time spent outside ( < 3.5 
 h day , table 2 ) . mean inhalation 
 exposure was also greater for children and mothers in urban environments 
 ( ec ) than for children ( p = 0.001 ) and mothers ( p < 0.001 ) in rural environments ( cj ) ( figure 4 ) . these differences between inhalation exposure 
 for ec and cj residents are more pronounced for pentachlorinated congeners , 
 such as pcb 118 , which are about 5-fold more concentrated inside ec 
 than cj homes ( figure 3 ) . in both locales , mono- to penta - chlorinated congeners represent 9193% of total 
 pcb inhalation exposure ( si , table s3 ) . coeluting congeners pcbs 40 + 41 + 71 and 44 + 47 + 65 , the who indicator 
 congener pcb 52 , and the non - aroclor pcb 11 were inhaled in the greatest 
 amounts by mothers , whereas congeners pcbs 61 + 70 + 74 + 76 , pcb 95 , and 
 pcbs 90 + 101 + 113 ( in addition to the above ) were inhaled at high rates 
 by children ( 0.60 g yr congener ) ( si , table s3 ) . notwithstanding 
 pcb 11 , cosine theta statistical comparisons ( 0.600.78 on 
 a scale of 0 to 1 , with 1 representing identical profiles ) show fair 
 agreement between aroclor 1248 and inhalation exposure profiles . mean airborne pcb concentrations , derived from harner 
 passive air 
 samplers deployed for 90 days ( homes ) or 45 days ( schools ) . indoor 
 school samples were normally distributed and are thus presented as 
 an arithmetic mean  se . other samples were log - normally distributed 
 and are presented as a geometric mean ( se ) . inhalation ( bar ) and dietary ( pie ) exposure by location and food 
 group excluding houses with extreme values . other  
 dietary sources include butter , fats and oils , margarine , and eggs . other  inhalation sources include time spent at locations 
 not measured directly , such as churches , places of work , and other 
 public areas . sum (  ) pcb dietary exposure 
 was greater than pcb inhalation exposure for most individuals 
 ( figure 4 ) , except for the ec household with 
 highest airborne pcb concentrations ( 74  40 ng m ) . dairy and meat contributed the greatest amount to ingested pcb , 
 depending on the age , location , and sex of the subjects ( figure 4 ) . meats contributed the greatest amount of pcbs 
 to dietary exposure in ec , whereas dairy contributed the greatest 
 amount of pcbs to dietary exposure in cj ( figure 4 ) . male children appear to ingest more pcbs than female children 
 or mothers ( figure 4 , si , table s3 ) . these differences arise from different food ingestion 
 rates for males vs females and for mothers vs children . we have estimated inhalation 
 ( pcb ) and dietary 
 ( pcb ) exposures for mother / child cohorts in east 
 chicago , indiana , and columbus junction , iowa . the scope of air sampling 
 performed here , via the aesop study , includes aroclor and non - aroclor , 
 lower - chlorinated congeners that have rarely been measured in exposure 
 assessments . the non - aroclor pcb 11 , for example , was present at about 
 100 ng m in many indoor environments . likewise 
 pcb 8 was present at concentrations ranging from 10 ng m to more than 400 ng m. neither of these congeners 
 have been measured in prior inhalation exposure studies ( table 3).the pcb inhalation rates for our subjects 
 ( 2.43 ( 0.38 ) to 12.0 ( 1.18)g yr ) are similar 
 to those for individuals living in urban areas in the united kingdom and china , but 
 are less than those estimated for individuals in contaminated environments 
 ( table 3 ) . previous estimates have been based 
 on 40 or fewer congeners and , among the lower - chlorinated congeners 
 ( mono- to pentachloro ) , often contain only the who indicators : pcb 
 28 , 52 , and 101 ( table 3 ) . in this study , other 
 lower - chlorinated congeners represent 7080% of mean pcb 
 inhalation exposure , including the potentially neurotoxic congeners 
 pcb 11 , 40 , 51 , and 95 . median statistics for [ pcb ] 
 are 
 provided for these studies , and exposure is estimated here as [ m )  16 m d  365 d yr and multiplied by 0.667(assuming 
 16 h d at home ) or 0.333 ( assuming 8 h d at schools / offices ) . who 
 indicator congeners include 
 pcb 28 , 52 , 101 , 138 , 153 , and 180 . congener profiles for inhalation exposure resemble aroclor 1248 
 with additional contributions from aroclor 1254 and the non - aroclor 
 pcb 11 . the latter congener is produced as a byproduct of paint pigment 
 manufacturing and is thus likely ubiquitous 
 in residential and commercial buildings , especially those with green , 
 yellow , or other organic paint pigments . given the presence of paint 
 in virtually all indoor environments , we expect these results to be 
 generalizable within the u.s . pcbs 40 + 41 + 71 , and 52 
 were also abundant in aesop study 
 homes . pcb 40 reduces cell dopamine content , but confirmation of other health effects is scarce . biological effects 
 of pcb 52 include potential tumor promotion , granule neuronal cell 
 death , and immune suppression . this pcb is , by far , the most abundant congener in the air of columbus 
 junction schools ( figure 3 ) and is inhaled 
 at the highest rates by cj children ( si , table s3 ) . dietary pcb exposure is often greater than inhalation 
 exposure , 
 but this difference may be less pronounced for lower - chlorinated congeners 
 which have higher volatility and less potential for bioaccumulation . our subjects have inhalation - to - diet exposure ratios that increase 
 with decreasing pcb chlorination . this ratio approaches 1:2 for the 
 tetrachlorinated pcbs 40 + 41 + 71 and 44 + 47 + 65 , and 52 ( si , table s3 ) , and may be greater than 1:1 for di- and trichlorinated 
 congeners not measured in diet ( e.g. , pcb 8 , 11 , 18 + 30 ) . dietary 
 pcb exposure estimated for residents of the united kingdom 
 ( 340 g yr ) , finland ( 438 g yr ) , and south korea ( 198 g yr ) are similar in scale to those reported here , but result from greater 
 contributions of grains and vegetables ( south korea ) and fish ( finland , 
 u.k . ) . here we calculate higher ambient inhalation 
 exposure in an urban 
 ( ec ) compared to a rural ( cj ) environment , based on differences in 
 airborne pcb concentrations . elsewhere we show that ec children 
 have blood enriched with lower - molecular weight pcbs relative to other 
 congeners , a finding that may denote increased inhalation exposure 
 for this demographic . however , we did 
 not see a significant difference between serum pcb concentrations 
 for ec and cj subjects . this finding 
 is likely driven by greater lifetime dietary exposure , as compared 
 to inhalation exposure , and higher rates of removal for lower congeners 
 ( often inhaled ) as compared to higher congeners ( often ingested ) . schools and other buildings of masonry construction are prone 
 to 
 pcb contamination , due to the presence of pcb - laden caulking and sealants . schools in the aesop study have 
 lower pcb concentrations than those reported for contaminated schools 
 and apartments in north america and europe ( table 3 ) . however , aesop study schools still account for 4653% 
 of inhalation exposure for children , and they demonstrate significantly 
 higher airborne pcb concentrations than do homes . as school districts 
 in the u.s . our results 
 demonstrate that both new and old school buildings have higher indoor 
 air pcb concentrations than do homes regardless of year of construction 
 or locale . a potentially important limitation of this analysis 
 includes the 
 use of imputed values for a portion ( 24% ) of inhalation exposure . 
 there may be some mothers , in particular , who work in buildings with 
 elevated pcb concentrations . we evaluated this possibility by documenting 
 subjects entire work history : none have worked in industries 
 with known pcb risks . other sources of uncertainty include pulmonary 
 absorption and inhalation rates , time - activity data , and pas methodology . populations , and are age- , 
 gender- , and weight - specific for each subject . however , especially 
 active individuals , for example , those that spend 4-fold greater time 
 at moderate activity levels , may have 1520% greater inhalation . we think 
 this is reasonable : pulmonary absorption should increase with koa , and even the low - koa congener pcb 11 has exhibited pulmonary absorption rates 
 of 99.8% . also unaddressed in our model is uncertainty in time activity data , which may alter inhalation exposure 
 by 1015% ( i.e. , if an individual living in a pcb - contaminated 
 home spends 5 fewer hours at home than reported ) . finally , as with 
 all pas - based studies , uncertainty in sampling rates affects estimated 
 pcb concentrations . fortunately , our indoor sampling rates have low 
 variability and agree well with values derived from depuration compounds . 
 furthermore , sampling rate uncertainty for more variable , outdoor 
 environments uncertainty in dietary exposure includes the use of older 
 tds data 
 sets ( 19941996 ) , which may have greater concentrations than 
 current food supplies , due to slight decadal decreases in environmental 
 pcb concentrations since the 1990s . ( 53 ) additionally , our dietary 
 estimates are limited to 40 congeners and may miss some relevant exposure 
 to less abundant congeners . the aesop study provides the first 
 congener - specific pcb inhalation 
 exposure estimates for ambient environments in north america . here we present inhalation exposure estimates for 201 congeners , the majority 
 of which have been excluded from previous inhalation exposure studies , 
 including the abundant congeners pcb 8 and 11 . the results of 293 
 indoor and outdoor pas measurements , analyzed across 201 congeners 
 at schools and homes , indicate higher pcb concentrations in 
 urban than in rural aesop study homes . the potentially neurotoxic 
 congeners pcbs 40 + 41 + 71 and 44 + 47 + 65 , and 52 were inhaled at the greatest 
 rates . in both study locales , pcb inhalation exposure was 
 greater for children than for mothers , due to 5- to 10-fold greater 
 pcb concentrations in schools than in homes . estimated pcb 
 dietary exposure was greater than pcb inhalation exposure 
 for all aesop study participants except a mother and a child in a 
 contaminated home in the urban locale . bloodborne pcb measurements 
 of the same cohorts provide the future 
 opportunity to evaluate relationships between dietary and inhalation 
 exposure and individual body burden .
polychlorinated 
 biphenyls ( pcbs ) are a group of 209 persistent 
 organic pollutants , whose documented carcinogenic , neurological , and 
 respiratory toxicities are expansive and growing . 
 however , pcb inhalation 
 exposure assessments have been lacking for north american ambient 
 conditions and lower - chlorinated congeners . 
 we assessed congener - specific 
 inhalation and dietary exposure for 78 adolescent children and their 
 mothers ( n = 68 ) in the airborne exposure to semi - volatile 
 organic pollutants ( aesop ) study . 
 congener - specific pcb inhalation 
 exposure was modeled using 293 measurements of indoor and outdoor 
 airborne pcb concentrations at homes and schools , analyzed via tandem 
 quadrupole gs - ms / ms , combined with questionnaire data from the aesop 
 study . 
 dietary exposure was modeled using canadian total diet survey 
 pcb concentrations and national health and nutrition examination survey 
 ( nhanes ) food ingestion rates . for pcb , 
 dietary exposure dominates . 
 for individual lower - chlorinated congeners ( e.g. , pcbs 40 + 41 + 71 , 52 ) , 
 inhalation exposure was as high as one - third of the total ( dietary+inhalation ) 
 exposure . 
 pcb inhalation ( geometric mean ( se ) ) was greater 
 for urban mothers ( 7.1 ( 1.2 ) g yr1 ) and 
 children ( 12.0 ( 1.2 ) g yr1 ) than for rural 
 mothers ( 2.4 ( 0.4 ) g yr1 ) and children ( 8.9 
 ( 0.3 ) g yr1 ) . 
 schools attended by aesop 
 study children had higher indoor pcb concentrations than did homes , 
 and account for the majority of children s inhalation exposure .