qaannaq , upernavik , ummannaq , qeqertarsuaq , ilulissat , sisimiut , nuuk , narsaq , tasiilaq and ittoqqor - toormitt  in the period from 19972006 ( fig . participants from nuuk during 20002002 were randomly selected from a cross - sectional study assessing legacy pop exposure on osteoporosis - related ultrasound bone measurements in greenlandic inuit women ( 29 ) , and the rest of the participants were randomly selected from projects in the human health program of the ongoing circumpolar amap ( 21,30,31 ) . map of greenland showing the different districts and sampling periods , including the serum pfaas median levels ( ng / ml ) for each district . the proposed protocols of the studies were accepted by the ethical committee for scientific investigations in greenland and all the participants gave written informed consent . the following compounds were analysed in serum samples : perfluoroheptanoic acid ( pfhpa ) , perfluorooctanoic acid ( pfoa ) , perfluorononanoic acid ( pfna ) , perfluorodecanoic acid ( pfda ) , perfluoroundecanoic acid ( pfuna ) , perfluorododecanoic acid ( pfdoa ) , perfluorotridecanoic acid ( pftra ) , perfluorohexane sulfonate ( pfhxs ) , perfluorooctane sulfonate ( pfos ) and perfluorooctane sulfonamide ( pfosa ) . the following compounds from wellington laboratories were used as surrogate standards : c8-pfoa , c4pfos and c2-pfda . instrumental analysis was performed by liquid chromatography - tandem mass spectrometry ( lc - ms - ms ) with electrospray ionization ( esi ) . the analytical method used here method performance was tested through participation in inter - laboratory comparison studies organized by the institute nationale de sant publique du qubec for amap ( 33 ) . satisfactory z - scores were obtained in the inter - laboratory comparison studies from our laboratory . serum concentration of pcb congeners cb99 , cb101 , cb105 , cb118 , cb128 , cb138 , cb153 , cb156 , cb170 , cb180 , cb183 and cb187 , and organochlorine pesticides including chlordanes , p , p-dichlorodiphenyldichloroethane ( p , p-dde ) , p , p-dichlorodiphenyltrichloroethane ( p , p-ddt ) , oxychlordane , hexachlorobenzene ( hcb ) , beta - hexachlorocyclohexane ( -hch ) , mirex and toxaphene were measured at the certified laboratory , le centre toxicologie , in sainte foy , quebec , canada ( 21,23,29,30 ) . the fatty acid profiles were determined in plasma phospholipids at the biology department of the university of guelph , ontario , canada ( 23,34 ) . the ratio between n-3 polyunsaturated fatty acids and n-6 fatty acids is known to be a strong indicator of seafood intake and thus is a good indicator of the relative consumption of traditional food versus imported food ( 35 ) . the statistical analysis of the data was performed in spss 13.0 ( spss inc . , half of the detection limit values were used in case of concentrations below the detection limit . based on the chemical structure , the analysed pfaas were grouped in perfluorosulfonated acids ( pfsas )  as in , the sum of pfos , pfhxs and pfosa  and perfluor - ocarboxylated acids ( pfcas ) , which were made up of the sum of pfhpa , pfoa , pfna , pfda , pfuna , pfdoa and pftra . the legacy pops were grouped in pcbs ( sum of 12 measured pcb congeners ) , pesticides ( sum of 8 measured organochlorine pesticides ) and legacy pops ( sum of 12 pcb congeners and 8 pesticides ) . due to the low number of samples collected from most districts and the different lifestyles among them ( 21 ) , the data from non - nuuk districts were grouped as pooled non - nuuk district data , and the subsequent data analysis was based on the comparison between nuuk and pooled non - nuuk district data . natural logarithm ( ln)-transformed data improved the normality and homogeneity of variance and the statistical analyses were performed on the ln - transformed data . pearson correlation analysis was performed to assess the bivariate correlation between life - style factors and both pfaas and legacy pops . previous studies reported a correlation between pfaa and both age and n-3/n-6 ratio ( 17,26,36 ) . therefore comparisons of means for pfaas between the districts and genders were also performed by the general linear model procedure under adjustment of age and n-3/n-6 . the following approaches were used : ( 1 ) univariate regression analyses , where age and n-3/n-6 were included individually in the model ; ( 2 ) multi - variate regression analyses , in which pfos , pfoa , sumpfsa sumpfca , age and n-3/n-6 were included and thereby mutually adjusted . multiple linear regression analysis was used to assess the relationship between serum pfaa levels and the serum level of legacy pops under adjustment of age and n-3/n-6 ratio . comparison of the biomarker of seafood intake ( n-3/n-6 ratio ) was also performed under adjustment of age since seafood intake is significantly correlated to age . time pfaa trend analyses were performed on 142 samples from nuuk . only time series with at least 4 years of data were included in the analysis . the analyses of temporal trends followed the procedures used in temporal trend assessments by the international council for the exploration of the sea , a method that employs a robust , regression - based analysis to detect temporal trends ( 37 ) . the total variation in the contaminant index values over time was divided into a linear and a non - linear component . log - linear regression analysis was applied to describe the linear component , and a simple , 3-point running mean smoother was applied to describe the non - linear component . the linear and non - linear components were tested by means of an anova . the time trend analysis was performed with pia , a statistic analytical tool developed for analysis of amap time trend data sets ( 38 ) . since pfaas was reported to be related to age ( 26 ) , age was also added as a covariate for the adjustment of age in the trend analysis . all participants were of inuit descent , defined as having more than 2 grandparents born in greenland . qaannaq , upernavik , ummannaq , qeqertarsuaq , ilulissat , sisimiut , nuuk , narsaq , tasiilaq and ittoqqor - toormitt  in the period from 19972006 ( fig . participants from nuuk during 20002002 were randomly selected from a cross - sectional study assessing legacy pop exposure on osteoporosis - related ultrasound bone measurements in greenlandic inuit women ( 29 ) , and the rest of the participants were randomly selected from projects in the human health program of the ongoing circumpolar amap ( 21,30,31 ) . map of greenland showing the different districts and sampling periods , including the serum pfaas median levels ( ng / ml ) for each district . the proposed protocols of the studies were accepted by the ethical committee for scientific investigations in greenland and all the participants gave written informed consent . the following compounds were analysed in serum samples : perfluoroheptanoic acid ( pfhpa ) , perfluorooctanoic acid ( pfoa ) , perfluorononanoic acid ( pfna ) , perfluorodecanoic acid ( pfda ) , perfluoroundecanoic acid ( pfuna ) , perfluorododecanoic acid ( pfdoa ) , perfluorotridecanoic acid ( pftra ) , perfluorohexane sulfonate ( pfhxs ) , perfluorooctane sulfonate ( pfos ) and perfluorooctane sulfonamide ( pfosa ) . the following compounds from wellington laboratories were used as surrogate standards : c8-pfoa , c4pfos and c2-pfda . instrumental analysis was performed by liquid chromatography - tandem mass spectrometry ( lc - ms - ms ) with electrospray ionization ( esi ) . the analytical method used here method performance was tested through participation in inter - laboratory comparison studies organized by the institute nationale de sant publique du qubec for amap ( 33 ) . satisfactory z - scores were obtained in the inter - laboratory comparison studies from our laboratory . serum concentration of pcb congeners cb99 , cb101 , cb105 , cb118 , cb128 , cb138 , cb153 , cb156 , cb170 , cb180 , cb183 and cb187 , and organochlorine pesticides including chlordanes , p , p-dichlorodiphenyldichloroethane ( p , p-dde ) , p , p-dichlorodiphenyltrichloroethane ( p , p-ddt ) , oxychlordane , hexachlorobenzene ( hcb ) , beta - hexachlorocyclohexane ( -hch ) , mirex and toxaphene were measured at the certified laboratory , le centre toxicologie , in sainte foy , quebec , canada ( 21,23,29,30 ) . the fatty acid profiles were determined in plasma phospholipids at the biology department of the university of guelph , ontario , canada ( 23,34 ) . the ratio between n-3 polyunsaturated fatty acids and n-6 fatty acids is known to be a strong indicator of seafood intake and thus is a good indicator of the relative consumption of traditional food versus imported food ( 35 ) . the statistical analysis of the data was performed in spss 13.0 ( spss inc . , half of the detection limit values were used in case of concentrations below the detection limit . based on the chemical structure , the analysed pfaas were grouped in perfluorosulfonated acids ( pfsas )  as in , the sum of pfos , pfhxs and pfosa  and perfluor - ocarboxylated acids ( pfcas ) , which were made up of the sum of pfhpa , pfoa , pfna , pfda , pfuna , pfdoa and pftra . the legacy pops were grouped in pcbs ( sum of 12 measured pcb congeners ) , pesticides ( sum of 8 measured organochlorine pesticides ) and legacy pops ( sum of 12 pcb congeners and 8 pesticides ) . due to the low number of samples collected from most districts and the different lifestyles among them ( 21 ) , the data from non - nuuk districts were grouped as pooled non - nuuk district data , and the subsequent data analysis was based on the comparison between nuuk and pooled non - nuuk district data . natural logarithm ( ln)-transformed data improved the normality and homogeneity of variance and the statistical analyses were performed on the ln - transformed data . pearson correlation analysis was performed to assess the bivariate correlation between life - style factors and both pfaas and legacy pops . previous studies reported a correlation between pfaa and both age and n-3/n-6 ratio ( 17,26,36 ) . therefore comparisons of means for pfaas between the districts and genders were also performed by the general linear model procedure under adjustment of age and n-3/n-6 . the following approaches were used : ( 1 ) univariate regression analyses , where age and n-3/n-6 were included individually in the model ; ( 2 ) multi - variate regression analyses , in which pfos , pfoa , sumpfsa sumpfca , age and n-3/n-6 were included and thereby mutually adjusted . multiple linear regression analysis was used to assess the relationship between serum pfaa levels and the serum level of legacy pops under adjustment of age and n-3/n-6 ratio . comparison of the biomarker of seafood intake ( n-3/n-6 ratio ) was also performed under adjustment of age since seafood intake is significantly correlated to age . time pfaa trend analyses were performed on 142 samples from nuuk . only time series with at least 4 years of data were included in the analysis . the analyses of temporal trends followed the procedures used in temporal trend assessments by the international council for the exploration of the sea , a method that employs a robust , regression - based analysis to detect temporal trends ( 37 ) . the total variation in the contaminant index values over time was divided into a linear and a non - linear component . log - linear regression analysis was applied to describe the linear component , and a simple , 3-point running mean smoother was applied to describe the non - linear component . the time trend analysis was performed with pia , a statistic analytical tool developed for analysis of amap time trend data sets ( 38 ) . since pfaas was reported to be related to age ( 26 ) , age was also added as a covariate for the adjustment of age in the trend analysis . the median age of the green - landic inuit in the study was 50 years , ranged from 18 to 73 years . the included inuit living in nuuk were older than those living in the pooled non - nuuk districts , in terms of both the separate genders and pooled gender data . it should be noted that data for only 5 males were included in the nuuk district data . no significant difference was found in the bmi and the seafood intake biomarker ( n-3/n-6 ) between nuuk and non - nuuk inuit . most participants ( 68.9% ) were smokers , but no difference was observed between districts . no gender differences were observed for age , bmi , n-3/n-6 and smoking status within nuuk and pooled non - nuuk districts ( p>0.06 ) ( table i ) . pfaa concentrations differed significantly between the studied inuit from nuuk and pooled non - nuuk districts . nuuk inuit had significantly higher pfaa levels than pooled non - nuuk inuit , both for the separate gender data and pooled data . serum levels of pfaas and legacy pops of greenlandic inuit participants p - value of nuuk vs. non - nuuk after adjustment for age and n-3/n-6 ; legacy pops is the summation of pcbs and pesticides ( pcbs+pesticides ) . two subjects from upernavik district had relatively high values of pfaas ( pfos : 91.8 and 74.9 ng / ml ; pfoa : 8.6 and 4.0 ng / ml ; pfsa : 101 and 83.5 ng / ml ; pfca:12.8 and 9.85ng / ml ) . the levels of legacy pops were generally higher for nuuk inuit compared to non - nuuk inuit . for the pooled gender data , levels of pcbs , pesticides and legacy pops for nuuk inuit were significantly higher than for pooled non - nuuk inuit ( table ii ) . however , after adjustment for age and n-3/n-6 , pcb levels were not significantly different between the nuuk district and pooled non - nuuk district for the separate genders , whereas pesticides differed between the 2 district groups for both genders . serum pfaa levels in male inuit were significantly higher than those in female inuit both before and after adjustment for age and n-3/ n-6 within both nuuk and pooled non - nuuk districts ( figure 2a , 2b ) . significantly higher levels of legacy pops for males were found in the pooled non - nuuk districts only , and a statistically insignificant tendency of higher legacy pops in nuuk males was observed , although the small sample size of nuuk males must be taken intoconsideration ( figure 2c ) . a ) pfsas ( pfos+pfhxs+pfosa ) ; b ) pfcas ( pfhpa+pfoa+pfna+pfda+pfuna+pfdoa+pftra ) ; c ) legacy pops ( pcbs+ pesticides ) . p - values were adjusted for age and n-3/n-6 . a significant but weakly positive correlation between age and serum pfaa levels ( r0.29 , p0.001 ) was observed in non - nuuk inuit . for the nuuk inuit , in general , pfaas were not significantly correlated to age ( supplementary table i a , www.ijch.fi ) . a relatively weak correlation between serum concentrations of pfsas and pfcas and n-3/n-6 ( r<0.27 , p<0.05 ) was observed for both nuuk and non - nuuk inuit ( supplementary table i a , www.ijch.fi ) . legacy pops significantly correlated with age ( r>0.42 , p<0.0001 ) and n-3/n-6 ( r>0.60 , p<0.0001 ) ( supplementary table i a , www.ijch.fi ) . positive correlations among pfaa levels with both age and seafood intake were also observed for both genders . in general , the correlations found in female inuit were higher than those in male inuit , while the correlations between age , n-3/n-6 and legacy pops between genders were similar ( supplementary table i b , www.ijch.fi ) . for male inuit , the correlation between n-3/n-6 and pfaas was weaker than that between legacy pops and n-3/n-6 ( supplementary table i b , www.ijch.fi ) . to explore whether the sources for the body burden of pfaas and legacy pops in green - landic inuit were identical , we analysed the correlation between serum pfaas and legacy pops . for the nuuk inuit , positive correlations between serum pfos , pfsas , pfcas and  legacy pops were observed . but after adjustment for age and seafood intake ( n-3/n-6 ) , the significant correlations of pfos and pfsas with legacy pops disappeared ( table iii ) . for the non - nuuk inuit , significant correlations between serum pfaas and legacy pops were observed both before and after adjustments for age and n-3/n-6 ( table iii ) . the correlation between pfaas and legacy pops was also different between genders . for the male nuuk inuit no correlations were observed , possibly because of the low number of males in the study ( n=5 ) . for non - nuuk males the significant correlation between pfaas and legacy pops disappeared after adjustment for age and n-3/ n-6 . for non - nuuk female inuit and for female inuit in general , serum pfaas significantly correlated to legacy pops both before and after adjustment for age and n-3/n-6 , whereas for nuuk females alone the significance disappeared upon adjustment ( table iii ) . association between serum pfcs and serum legacy pops legacy pop is the regression coefficient of pfaas to legacy pops . temporal trend analysis was performed for the district of nuuk , where a sufficient number of samples were available for the period 19982005 . as shown in table iv , pfos level and pfca level showed 2.2% and 7.1% yearly increasing trends , respectively , for female inuit . for the pooled gender data , 28% , 28% , 10% , 13% and 15% yearly increasing trends were found for pfna , pfda , pfdoa , pftra and pfcas , respectively . the trends were statistically significant ( p<0.05 ) . however , after adjustment for age , the significant trend disappeared ( table iv ) . no significant time trend was observed for the serum level of pfoa and pfsa before and after adjustment for age ( table iv ) , and neither for pfhxs , pfosa , pfhpa or pfuna ( data not shown ) . time trend of serum concentrations ( ng / ml ) of pfaas in greenlandic inuit from nuuk in the period 19982005 slope : yearly difference ; values in bold indicate that the trend is statistically significant . time trend analysis was not performed for the male inuit because there were only 5 males studied in nuuk . for other test pfaas , no time trend was observed . the median age of the green - landic inuit in the study was 50 years , ranged from 18 to 73 years . the included inuit living in nuuk were older than those living in the pooled non - nuuk districts , in terms of both the separate genders and pooled gender data . it should be noted that data for only 5 males were included in the nuuk district data . no significant difference was found in the bmi and the seafood intake biomarker ( n-3/n-6 ) between nuuk and non - nuuk inuit . most participants ( 68.9% ) were smokers , but no difference was observed between districts . no gender differences were observed for age , bmi , n-3/n-6 and smoking status within nuuk and pooled non - nuuk districts ( p>0.06 ) ( table i ) . pfaa concentrations differed significantly between the studied inuit from nuuk and pooled non - nuuk districts . nuuk inuit had significantly higher pfaa levels than pooled non - nuuk inuit , both for the separate gender data and pooled data . serum levels of pfaas and legacy pops of greenlandic inuit participants p - value of nuuk vs. non - nuuk after adjustment for age and n-3/n-6 ; legacy pops is the summation of pcbs and pesticides ( pcbs+pesticides ) . two subjects from upernavik district had relatively high values of pfaas ( pfos : 91.8 and 74.9 ng / ml ; pfoa : 8.6 and 4.0 ng / ml ; pfsa : 101 and 83.5 ng / ml ; pfca:12.8 and 9.85ng / ml ) . the levels of legacy pops were generally higher for nuuk inuit compared to non - nuuk inuit . for the pooled gender data , levels of pcbs , pesticides and legacy pops for nuuk inuit were significantly higher than for pooled non - nuuk inuit ( table ii ) . however , after adjustment for age and n-3/n-6 , pcb levels were not significantly different between the nuuk district and pooled non - nuuk district for the separate genders , whereas pesticides differed between the 2 district groups for both genders . serum pfaa levels in male inuit were significantly higher than those in female inuit both before and after adjustment for age and n-3/ n-6 within both nuuk and pooled non - nuuk districts ( figure 2a , 2b ) . significantly higher levels of legacy pops for males were found in the pooled non - nuuk districts only , and a statistically insignificant tendency of higher legacy pops in nuuk males was observed , although the small sample size of nuuk males must be taken intoconsideration ( figure 2c ) . a ) pfsas ( pfos+pfhxs+pfosa ) ; b ) pfcas ( pfhpa+pfoa+pfna+pfda+pfuna+pfdoa+pftra ) ; c ) legacy pops ( pcbs+ pesticides ) . a significant but weakly positive correlation between age and serum pfaa levels ( r0.29 , p0.001 ) was observed in non - nuuk inuit . for the nuuk inuit , in general , pfaas were not significantly correlated to age ( supplementary table i a , www.ijch.fi ) . a relatively weak correlation between serum concentrations of pfsas and pfcas and n-3/n-6 ( r<0.27 , p<0.05 ) was observed for both nuuk and non - nuuk inuit ( supplementary table i a , www.ijch.fi ) . legacy pops significantly correlated with age ( r>0.42 , p<0.0001 ) and n-3/n-6 ( r>0.60 , p<0.0001 ) ( supplementary table i a , www.ijch.fi ) . positive correlations among pfaa levels with both age and seafood intake were also observed for both genders . in general , the correlations found in female inuit were higher than those in male inuit , while the correlations between age , n-3/n-6 and legacy pops between genders were similar ( supplementary table i b , www.ijch.fi ) . for male inuit , the correlation between n-3/n-6 and pfaas was weaker than that between legacy pops and n-3/n-6 ( supplementary table i b , www.ijch.fi ) . to explore whether the sources for the body burden of pfaas and legacy pops in green - landic inuit were identical , we analysed the correlation between serum pfaas and legacy pops . for the nuuk inuit , positive correlations between serum pfos , pfsas , pfcas and  legacy pops were observed . but after adjustment for age and seafood intake ( n-3/n-6 ) , the significant correlations of pfos and pfsas with legacy pops disappeared ( table iii ) . for the non - nuuk inuit , significant correlations between serum pfaas and legacy pops were observed both before and after adjustments for age and n-3/n-6 ( table iii ) . for the male nuuk inuit no correlations were observed , possibly because of the low number of males in the study ( n=5 ) . for non - nuuk males the significant correlation between pfaas and legacy pops disappeared after adjustment for age and n-3/ n-6 . for non - nuuk female inuit and for female inuit in general , serum pfaas significantly correlated to legacy pops both before and after adjustment for age and n-3/n-6 , whereas for nuuk females alone the significance disappeared upon adjustment ( table iii ) . association between serum pfcs and serum legacy pops legacy pop is the regression coefficient of pfaas to legacy pops . temporal trend analysis was performed for the district of nuuk , where a sufficient number of samples were available for the period 19982005 . as shown in table iv , pfos level and pfca level showed 2.2% and 7.1% yearly increasing trends , respectively , for female inuit . for the pooled gender data , 28% , 28% , 10% , 13% and 15% yearly increasing trends were found for pfna , pfda , pfdoa , pftra and pfcas , respectively . however , after adjustment for age , the significant trend disappeared ( table iv ) . no significant time trend was observed for the serum level of pfoa and pfsa before and after adjustment for age ( table iv ) , and neither for pfhxs , pfosa , pfhpa or pfuna ( data not shown ) . time trend of serum concentrations ( ng / ml ) of pfaas in greenlandic inuit from nuuk in the period 19982005 slope : yearly difference ; values in bold indicate that the trend is statistically significant . time trend analysis was not performed for the male inuit because there were only 5 males studied in nuuk . the range observed for serum pfos and pfoa in all the greenlandic districts in the present study corresponded to the range observed in european biomonitoring studies of general populations ( 14 ) although the pfoa was found slightly lower in inuit ( 11,14 ) . the serum pfos level of nuuk inuit were comparable to those observed in europeans from sweden and from northern bavaria , germany , while non - nuuk inuit had a lower level of pfos  similar to that of europeans in southern bavaria , germany , and in tarragona , spain ( 14 ) . the median serum pfos and pfoa concentrations in male greenlandic inuit were lower than the plasma levels of pfos and pfoa in danish men ( 39 ) . very few data are available for pfaa serum concentrations from other arctic locations ; the literature data that are available are summarized in table v. the range of mean concentrations of pfos and pfoa in the other arctic studies were 9.336.9 ng / ml and 1.03.4 ng / ml , respectively , while the mean concentrations of pfos and pfoa of green - landic inuit reported in the present study were 33.3 ng / ml and 2.3 ng / ml , respectively ( table v ) . the size of our data set is larger than most of the other arctic data . moreover , both male and female samples were included in the present study , thus avoiding the bias that could be generated by only including serum samples from one gender . the pfos mean concentration ( 33.3 ng / ml ) of the greenlandic inuit in this study was slightly higher than the value ( 25.7 ng / ml ) reported by chateau - degat et al . , which also included male and female inuit ( 40 ) . pfos concentrations reported in other arctic studies including relatively few female subjects were generally lower than the pfos levels of green - landic inuit observed in the present study ( table v ) . however , the mean pfoa level of the pooled greenlandic inuit in our study was comparable to the other reported arctic studies ( table v ) . we did observe gender differences in pfaa levels ; greenlandic inuit within the same district tended to be in accordance with the majority of studies on gender dependency of pfos serum concentrations ( 14 ) , with higher levels in male donors . this gender difference has been partially explained by increased excretion through menstrual flow ( 41 ) , transplacental transfer of pfos and other pfaas to the developing foetus and transfer via milk during breastfeeding in females of younger ages ( 42 ) . other explanations of lower levels in women rely on higher renal clearance of pfaas in women and longer half - lives in males , based on studies of laboratory rodents ( 14 ) . but the last assumption might not be completely true , as better renal clearance in females was not observed in other species ( dogs , rabbits and mice ) ( 14 ) , and no sex difference was found in the renal clearance of humans ( 41 ) . moreover , our data do not support the hypothesis that the higher pfaa levels in males were due to a higher intake of traditional marine food , because males and females had similar seafood intake ( n-3/n-6 ) . moreover , after adjustment for age and n-3/n-6 , the pfaa differences between genders were still statistically significant . we suggest that other sources must contribute to the higher levels of pfaas in male greenlandic inuit . since pfaas are very persistent , the body burden of pfaas may increase with age . studies investigating the dependency of pfaa serum concentrations on age have given inconsistent results , with some studies reporting statistically significant correlations ( 17,36 ) , and others not observing any correlations ( 16,43 ) . in this study , no correlation was observed between pfaas and age for nuuk inuit , while significant correlation was found for non - nuuk inuit . because the median age of non - nuuk inuit was lower than that of nuuk inuit in this study , this discrepancy may be related to the fact that the lifestyle of younger individuals could pose a higher chance of exposure to pfaas ( via clothing or consumption of food items that have been in close contact with packaging containing pfcs ) ( 26,44 ) . dallaire et al . also observed an age dependency of pfos plasma concentrations , with older individuals having higher concentrations ( 26 ) . this was partially explained by the fact that marine food intake also increases with age . consumption of traditional food has been suggested to be an important source of pfaa exposure for indigenous arctic populations ( 28,45 ) . indicated that consumption of fish and marine mammals , male gender and age were the strongest predictors of pfos plasma concentrations in the investigated inuit population . however , diet , gender and age could account for only 28% of the variation in pfos concentrations ( 26 ) . in the present study , we observed that the correlation between pfaas and seafood intake was weaker than the correlation between legacy pops and seafood intake , suggesting that seafood intake might be the main source for legacy pops and to a lesser degree for pfaas . thus other factors may contribute to pfaa exposure in the inuit populations , such as consumer products ( e.g. , impregnation spray for outdoor clothing ) and different indoor sources ( e.g. , house dust in carpeted houses ) . moreover , our data are supported by the study of tittlemier and co - workers , which suggested that a diet based on traditional foods does not contribute to higher body burdens of pfaas to the same degree as has been observed for legacy pops ( 27 ) . similarly to the data reported by fromme and co - workers ( 36 ) , the correlation between pfaas and marine food intake observed for male inuit in the present study was weaker than that observed for female inuit , suggesting that sources other than n-3/n-6 might also contribute to the higher pfaa levels in male inuit . moderately positive correlations were observed between legacy pops and age as well as n-3/n-6 , similar to previous reports ( 21,35,46 ) . in male inuit , the correlation between legacy pops and n-3/n-6 was stronger than the correlation between pfaas and n-3/n-6 , further suggesting that other sources might play a more important role than seafood intake in the higher body levels of pfaas in greenlandic male inuit as observed in the present study . no significant association was observed between pfaas and legacy pops , suggesting that sources of serum pfaas and legacy pops in nuuk inuit might vary . for non - nuuk inuit , significant correlations between serum pfaas and legacy pops were observed both before and after adjustments for age and n-3/n-6 , suggesting that there might be common sources for the body burden of pfaas and legacy pops in non - nuuk inuit . the correlation between pfaas and legacy pops was also different between genders ; no correlation was found for male inuit and a significant correlation was observed for females , further suggesting that sources other than seafood intake played an important role in the body burden of pfaas and legacy pops for male greenlandic inuit . overall , our data indicate that the sources contributing to the body burden of pfaas and legacy pops might be different for nuuk inuit when compared to non - nuuk inuit . further studies are needed to clarify the pfaa and legacy pop exposure routes of green - landic inuit . for female nuuk inuit , we observed an age - dependent , increasing trend of pfos and pfcas . we also observed increasing , age - dependent trends for pfna , pfda , pfdoa and pftra in all nuuk inuit during the period between 1998 and 2005 . however , we can not conclude that there was an increasing trend of pfaas in nuuk inuit during 19982005 , since the significant trend disappeared upon adjustment forage and only 4 years of data series were used in the present study . however , neither did we observe an obvious decreasing trend for pfaas in nuuk inuit . further research including more time series is needed to study the time trend of pfaas in greenlandic inuit . in conclusion , the levels of pfos and pfoa of greenlandic inuit were comparable to those found in european populations and were similar to , or slightly higher than , those of other arctic populations . the pfaa serum levels differed between the 2 district groups , with higher levels found in the nuuk district than the pooled non - nuuk districts . within the districts , sources for the body burden of pfaas and legacy pops in greenlandic inuit might differ and sources other than seafood intake should be taken into consideration when assessing the body levels of pfaas in greenlandic inuit , especially for male inuit . an age - dependent , but no obvious increasing trend of serum pfaas in nuuk was observed during 19982005 .
objectivesperfluoroalkyl acids ( pfaas ) have been detected in human blood , breast milk and umbilical cord blood across the globe . 
 pfaas do accumulate in the marine food chain in arctic regions . in greenland , 
 increasing pfaa concentrations were observed during 19822006 in ringed seals and polar bears . 
 however , until now , no data have been reported for pfaas in greenlandic inuit . 
 this study assesses the level and temporal trend of serum pfaas in greenlandic inuit.study designcross - section and temporal time trend survey.methodsserum pfaa levels were determined in 284 inuit from different greenlandic districts using liquid chromatography - tandem mass spectrometry with electrospray ionization . the temporal time trend of serum pfaas in nuuk inuit during 19982005 and the correlation between serum pfaas and legacy persistent organic pollutants ( pops ) were explored.resultsserum pfaa levels were higher in nuuk inuit than in non - nuuk inuit . 
 within the same district , higher pfaa levels were observed for males . 
 an age - dependent , increasing trend of serum pfaa levels in the period from 19982005 was observed for nuuk inuit . for the pooled gender data , 
 no significant association between pfaas and legacy pops was observed for nuuk inuit while for non - nuuk inuit this correlation was significant . 
 no correlation between pfaas and legacy pops was found for male inuit , whereas significant correlation was observed both for pooled female inuit and for non - nuuk inuit females.conclusionswe suggest that sources other than seafood intake might contribute to the observed higher pfaa levels in nuuk inuit compared to the pooled non - nuuk inuit.1