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

Abstract

Introduction

POP biomonitoring programs are useful for exposure assessment, to analyze patterns, and to evaluate policies. However, population-representative surveys are scarce and heterogeneous. Reports on time trends in representative samples using the same methods are rare.

Objectives

To analyze the distribution of serum concentrations of 19 POPs in the general population of Barcelona city in 2006, and to compare it with the distribution in 2002.

Methods

231 participants in the Barcelona Health Survey were interviewed face-to-face, gave blood, and underwent a physical exam. Density plots (“POP Geoffrey Rose curves”) were used to represent the full population distribution of each compound.

Results

Eight POPs 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. The minimum number of POPs detected in one person was 5, and 72% of the population accumulated ≥ 10 compounds. p,p′-DDE and HCB showed the highest concentrations (median = 219 and 109 ng/g lipid, respectively). Concentrations decreased by 34–56% from 2002 to 2006. The decrease was similar in women and men, and in all age groups/birth cohorts. It was larger with increasing BMI; for p,p′-DDT, HCB and β-HCH the decrease in obese individuals was 31–44 percentage points larger than in subjects with normal weight. The distribution of POP concentrations was always switched towards higher values in women than men. POP levels also differed significantly by age, body mass index, weight gain, birth place and social class, but not by parity and breastfeeding. The two younger cohorts had a higher DDT/DDE ratio than the oldest cohort.

Conclusion

Although human POP contamination remains common in the city of Barcelona, concentrations decreased significantly in 4 years. Our approach suggests innovative ways to conceive, analyze and present results for other monitoring programs.

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.