Distribution of blood concentrations of persistent organic pollutants in a representative sample of the population of Barcelona in 2006, and comparison with levels in 2002
Highlights
► Eight of the 19 POPs analyzed were (each) detected in > 80% of the study subjects. ► The minimum number of POPs detected in one person was 5. ► There were large interindividual differences in concentrations. ► POP concentrations decreased 34–56% in Barcelona city in 4 years. ► Our “POP Geoffrey Rose curves” emphasize the population nature of the problem.
Introduction
Persistent organic pollutants (POPs) comprise a large variety of toxic substances such as hexachlorobenzene (HCB), hexachlorocyclohexanes (HCHs), dioxins, dichlorodiphenyltrichloroethane (DDT) and its metabolites (notably, dichlorodiphenyldichloroethene, DDE), and polychlorinated biphenyls (PCBs). POPs are highly lipophilic and resistant to degradation; they thus accumulate in adipose tissue and in organs such as liver, brain, or pancreas (WHO, 2003). Many human populations are exposed to POP mixtures over the lifecourse, usually at low doses (Luzardo et al., 2009). A variety of studies have shown that POPs may adversely influence health and well-being: they contribute to cause infertility, birth defects, learning disabilities, endocrine disruption, diabetes, several cancers, Alzheimer's and Parkinson's disease, and other neurological, gynecological and immunological disorders (Alonso-Magdalena et al., 2011, Casals-Casas and Desvergne, 2011, Diamanti-Kandarakis et al., 2009, Kaiser, 2005, La Merrill and Birnbaum, 2011, Schug, 2011, Soto and Sonnenschein, 2011, UNEP (United Nations Environment Programme), 2002). However, numerous uncertainties exist on the health effects of chronic exposure to POPs in the general population (Henkler and Luch, 2011, Hernández et al., 2009, Lee et al., 2009, Myers et al., 2009). To decrease such uncertainties and appropriately protect the health of citizens, better knowledge on the levels and trends of contamination of the population is essential.
Most POPs are presently targeted for elimination or reduction. Legal instruments as the Stockholm Convention encourage countries to integrate population-based surveillance of POP levels in humans within their health monitoring systems (Porta and Zumeta, 2002, UNEP (United Nations Environment Programme Chemicals), 2005). POP monitoring programs are useful for exposure assessment, to analyze trends and patterns of contamination, and to evaluate the effectiveness of policies aimed at decreasing exposure. However, worldwide, comprehensive monitoring of human contamination by POPs is scarce, fragmented and heterogeneous. Methodological characteristics of studies vary largely, including selection of participants, sociodemographic information, chemical and statistical methods, and frameworks for interpretation of results (Porta et al., 2008b, Porta et al., 2009a). For example, the full range of POP concentrations is often overlooked, and little attention is paid to the characteristics of the distribution of the concentrations (e.g., differences across subgroups in kurtosis, skewness, and coefficient of variation) (Porta et al., 2008b, Porta et al., 2010a). Also, national studies monitoring human exposure to POPs do not usually include data on parity and breastfeeding (Dewailly et al., 1996, Tajimi et al., 2004). Another example of a variable that is not usually collected in population biomonitoring studies is weight change, which may alter blood lipid levels and bias estimates of exposure to lipophilic compounds like POPs. As we shall see below, the influence of parity, breastfeeding and weight change was assessed in the present study.
As in other countries, in Spain most POPs were banned during the 1970s, and levels of some of them have decreased (Porta et al., 2008a). However, uncertainties abound, and the only two Spanish studies based on representative samples of a population detected a substantial number of compounds in over 85% of citizens (Zumbado et al., 2005, Porta et al., 2010b, Henríquez-Hernández et al., 2011, Porta et al., 2012). In 2006, the Public Health Agency of Barcelona conducted the fifth Barcelona Health Survey (BHS), which included a physical examination and, for the first time, blood drawing – explicitly conceived for POPs monitoring – in a sample of participants; serum concentrations of 19 POPs were thus determined in 231 subjects (Porta et al., 2009a). In 2002, POP concentrations were analyzed in the Catalan Health Survey (CHS); based on a representative sample of the population of Catalonia (Porta et al., 2010b), it included a subsample of individuals representative of the city of Barcelona. Therefore, for the first time in Spain, we could assess trends in POP levels in Barcelona measured in an identical way. Reports on POP time trends in representative samples using the same methods are also extremely rare worldwide.
The aim of the present study was, firstly, to analyze the distribution of serum concentrations of 19 POPs in the non-institutionalized adult population of Barcelona city, and its main socio-demographic predictors; and, secondly, to compare the concentrations of POPs analyzed in the BHS with the concentrations in individuals from Barcelona studied four years earlier in the CHS.
Section snippets
Study population and health interview survey
The study population of the Barcelona Health Survey of 2006 (BHS) has been described in detail elsewhere (Porta et al., 2009a, Rodríguez-Sanz et al., 2008). Briefly, at the end of the interview the study monitors offered BHS participants ≥ 15 years old to take part in the POP study (Porta et al., 2009a); the youngest person who actually participated in the POP study was 18 years old. Subsequently, a nurse personally interviewed each person who accepted to participate in the POP study, measured the
Results
Eight of the 19 POPs analyzed were each detected in > 80% of the study subjects: p,p′-DDT, p,p′-DDE, PCB congeners 118, 138, 153 and 180, HCB and β-HCH. p,p′-DDE was detected and quantified in all samples (Table 2, Fig. 1). The percentage of detection for the other 11 analytes ranged between 1% and 65% (Table 2 of Supplementary Material). Thus, all 19 POPs were detected. No individual was free from POPs: the smallest number detected in one person was 5 compounds, and the largest, 15 POPs. 72% of
Discussion
Eight POPs were each detected in > 80% of the study subjects, and no individual was free from POPs; the smallest number detected in one person was 5 compounds, while ten or more compounds were detected in 72% of the population. However, from 2002 to 2006 serum concentrations of POPs decreased 34–56% in Barcelona city (Porta et al., 2010b).
In the BHS a pattern of progressive “flattening” of the POP distributions with increasing age was also seen, as previously in the CHS (Porta et al., 2010b).
Conclusions
Although all POPs analyzed were banned decades ago, human contamination remains common in the city of Barcelona, as elsewhere. Eight of the 19 POPs analyzed were (each) detected in > 80% of the study subjects, the minimum number of POPs detected in one person was 5, and there were large interindividual differences in concentrations. However, POP concentrations decreased 34–56% in 4 years.
While scarce and heterogeneous worldwide, population-based surveys on the distribution of POP concentrations
Conflicts of interest
The authors declare they have no competing financial interests.
Acknowledgements
Supported in part by research grants from the Department of Health, Government of Catalonia; ‘Red temática de investigación cooperativa de centros en Cáncer’ (C03/10); ‘Red temática de investigación cooperativa de centros en Epidemiología y salud pública’ (C03/09); and CIBER de Epidemiología, Instituto de Salud Carlos III, Ministry of Health, Government of Spain. The authors gratefully acknowledge technical and scientific assistance provided by Joan Guix, Montserrat Guillén, Elisa Puigdomènech,
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