Relative effects of educational level and occupational social class on body concentrations of persistent organic pollutants in a representative sample of the general population of Catalonia, Spain
Introduction
POPs are highly lipophilic and degradation-resistant synthetic chemicals, which essentially originate from the production and use of organochlorine and other synthetic compounds. They bioaccumulate in the environment, food webs and living organisms, and contribute to cause severe health effects, even at concentrations traditionally deemed low (Alonso-Magdalena et al., 2011, Bergman et al., 2013, Department of Health and Human Services, 2009, Engel and Wolff, 2013, Henkler and Luch, 2011, NRC (National Research Council) and Committee on Human Biomonitoring for Environmental Toxicants, 2006, Porta, 2012, Porta et al., 2008a, Porta et al., 2012b, Schug et al., 2013, Stein, 2012, Thayer and Kuzawa, 2011, Thornton et al., 2002, Vandenberg et al., 2012, WHO (World Health Organization), 2003, Woodruff et al., 2010, Wu et al., 2012, Yang et al., 2012). Exposed to such agents throughout life, mostly from the ingestion of fatty parts of animal foods, virtually all humans store POP mixtures in fat tissues. Although some POPs were prohibited decades ago – and their concentrations thus decreased – human exposure, contamination and clinical effects remain relevant (Bergman et al., 2013, Department of Health and Human Services, 2009, Institute of Medicine, 2003, NRC (National Research Council) and Committee on Human Biomonitoring for Environmental Toxicants, 2006, Porta et al., 2008a, Porta et al., 2012b, Quinn and Wania, 2012, Quinn et al., 2011). Body concentrations of POPs are known to often be associated with age, body mass index (BMI), and, in women, also with parity (Agudo et al., 2009, Porta et al., 2008a, Porta et al., 2010, Porta et al., 2012b, Quinn and Wania, 2012, Quinn et al., 2011, Wolff et al., 2005). Some relationships have also been observed between POP concentrations and socioeconomic variables (Chao et al., 2010, Freire et al., 2011, Morrens et al., 2012, Porta et al., 2008a, Porta et al., 2012a, Vrijheid et al., 2012).
Although some mixed evidence exists, reasons for differences in internal body concentrations of persistent organic pollutants (POPs) across socioeconomic groups are largely unknown worldwide. In spite of the involvement in health disorders of both environmental pollutants and social factors, there are wide gaps in knowledge of the influence of socioeconomic position on human contamination by POPs and other pollutants (Bergman et al., 2013, Borrell et al., 2004a, Davey Smith et al., 1998, Martikainen et al., 2007, Morrens et al., 2012, NRC (National Research Council) and Committee on Human Biomonitoring for Environmental Toxicants, 2006, Porta et al., 2008a, Porta et al., 2012a, Subramanyam et al., 2013, Thayer and Kuzawa, 2011). Some evidence from studies based on non-representative samples indicates that such contamination does not affect all social and educational groups homogeneously; rather, some compounds seem to contaminate more intensely the more disadvantaged groups, generating a potentially unfair and perhaps avoidable gradient of inequalities in health (Brown, 1995, Freire et al., 2011, Hoffmann et al., 2009, Porta et al., 2008a). Even so, it has seldom been assessed to what extent structural differences among social groups in age and body weight explain their differences in POP contamination. Evidence on the relationships between social factors and human concentrations of environmental pollutants can also lead to a better understanding of health patterns by social class and educational level (Davies et al., 1972, Morrens et al., 2012).
Socioeconomic position is often related to environmental and occupational exposures, other living conditions, diet and lifestyle (Freire et al., 2011, Glynn et al., 2007, Ibarluzea et al., 2011, León-Muñoz et al., 2012, López-Azpiazu et al., 2003, Mesas et al., 2012, Rothman et al., 2011). Though commonly related, the nature and health effects of education and social class are different, sometimes outcome specific, and they cannot be used interchangeably: they measure different phenomena and act through different mechanisms (Martikainen et al., 2007, Schnittker, 2004, Thayer and Kuzawa, 2011). In addition to their potential to explain part of the population variation in human contamination by POPs, social class and education are also common possible confounders of associations between POPs and epidemiologic factors.
It is thus somewhat surprising that the evidence on the possible relation between indicators of socioeconomic position and human POP concentrations is so scant in studies based on representative samples of the general healthy population. To date, only reports from the United States (NRHEEC) (Department of Health and Human Services, 2009) and Germany (GerEs) (Becker et al., 2002) have assessed the relationship between body POP concentrations and ethnicity or socioeconomic status, respectively, in such samples.
Therefore, the present study aimed to investigate the separate and combined effects of occupational social class and educational level on body concentrations of several POPs in a representative sample of the general population of Catalonia, Spain. Special attention was paid to assess to what extent important characteristics of social groups, as age and body mass index, explain differences in internal contamination by POPs.
Section snippets
Study population
The study population has been described in detail elsewhere (Porta et al., 2010). Briefly, participants in the Catalan Health Interview Survey (CHIS 2002) aged 18–74 years old (N = 6243) were offered to take part in a health examination, which included a physical exam, a supplementary interview, and the collection of urine and blood samples. A total of 1374 individuals participated in the health examination during 2002. Trained nurses recorded the weight and height, and the corresponding body mass
Results in women
In women, the number of POPs detected per person showed no significant differences by social class. However, the number of POPs detected per person with concentrations in the upper quartile did show a significant relation with social class. The percentage of women without any POP with concentrations over the 75th percentile was higher in class I (61.1%) than in class V (14.7%) (p-value = 0.001). Moreover, the number of POPs detected per person and the number of compounds with concentrations in
Discussion
In unadjusted analyses, the percentage of individuals – men and women – with all eight POPs detected was higher in the groups with lower level of education, but there were no differences by social class. The percentage of subjects with one or more POPs with high concentrations was also higher among participants with less education and, among women only, in less affluent social classes (Fig. 4). In women, higher median crude (unadjusted) concentrations of all eight POPs were found with
Conclusions
Crude (unadjusted) concentrations were higher in women and men with lower education, and in women, but not men, in the less affluent social class. Educational level influenced blood concentrations of POPs more than occupational social class, especially in men. In women, POP concentrations were mainly explained by age/birth cohort, BMI and parity. In men, while concentrations were also mainly explained by age/birth cohort and BMI, social class showed some positive associations (higher POP levels
Conflicts of interest
The authors declare they have no competing financial interests.
Acknowledgements
The study was supported by research grants from the Government of Catalonia (2009 SGR 1350) and CIBER de Epidemiología y Salud Pública (CIBERESP), Instituto de Salud Carlos III, Government of Spain. The authors thank Fernando Rodríguez-Artalejo, Jesús Vioque, Julia Wärnberg, Natalia Salcedo, Eva Morales, Sílvia Santaularia and Yolanda Rovira for scientific and technical advice. Special thanks are due to participants in the survey, without whom this study would not have been possible.
References (72)
- et al.
Polychlorinated biphenyls in Spanish adults: determinants of serum concentrations
Environ Res
(2009) - et al.
German Environmental Survey 1998 (GerES III): environmental pollutants in blood of the German population
Int J Hyg Environ Health
(2002) - et al.
Calculation of body “total lipid” concentrations for the adjustment of persistent organohalogen toxicant measurements in human samples
Chemosphere
(2007) - et al.
Social class and self-reported health status among men and women: what is the role of work organisation, household material standards and household labour?
Soc Sci Med
(2004) Race, class and environmental health: a review and systematization of the literature
Environ Res
(1995)- et al.
Concentrations of polybrominated diphenyl ethers in breast milk correlated to maternal age, education level, and occupational exposure
J Hazard Mater
(2010) - et al.
Relationship between occupational social class and exposure to organochlorine pesticides during pregnancy
Chemosphere
(2011) - et al.
Empirical analyses of the influence of diet on human concentrations of persistent organic pollutants: a systematic review of all studies conducted in Spain
Environ Int
(2011) - et al.
Childhood social position and associations between environmental exposures and health outcomes
Int J Hyg Environ Health
(2009) - et al.
Sociodemographic, reproductive and dietary predictors of organochlorine compounds concentrations in pregnant women in Spain
Chemosphere
(2011)
Serum levels of organochlorine pesticides in healthy adults from five regions of Spain
Chemosphere
Adherence to the Mediterranean diet pattern has declined in Spanish adults
J Nutr
Social distribution of internal exposure to environmental pollution in Flemish adolescents
Int J Hyg Environ Health
Human contamination by environmental chemical pollutants: can we assess it more properly?
Prev Med
Differences in body concentrations of organochlorine compounds by occupational social class in pancreatic cancer
Environ Res
Monitoring concentrations of persistent organic pollutants in the general population: the international experience
Environ Int
Correcting body concentrations of organochlorine compounds by lipids: alternatives to the organochlorine/total lipids ratio
Environ Int
Distribution of blood concentrations of persistent organic pollutants in a representative sample of the population of Catalonia
Environ Int
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
Sci Total Environ
Number of persistent organic pollutants detected at high concentrations in a general population
Environ Int
The importance of a gender perspective in health interview surveys
Gac Sanit
Predictors of organochlorines in New York City pregnant women, 1998–2001
Environ Res
Body concentrations of polychlorinated dibenzodioxins and dibenzofurans and PCBs in the general population living near an urban waste treatment plant in Biscay, Basque Country
Chemosphere
Endocrine disruptors in the etiology of type 2 diabetes
Nat Rev Endocrinol
Statistical methods in medical research
Biomonitoring in Greenland: human biomarkers of exposure and effects — a short review
Rural Remote Health
Inequalities in health related to social class in women. What is the effect of the measure used?
Gac Sanit
Effect of socioeconomic status on exposures to polychlorinated biphenyls (PCBs) and dichlorodiphenyldichloroethylene (DDE) among pregnant African-American women
Arch Environ Health
The social determinants of health: coming of age
Annu Rev Public Health
Education and occupational social class: which is the more important indicator of mortality risk?
J Epidemiol Community Health
The role of social class in human pesticide pollution
Am J Epidemiol
Fourth National Report on Human Exposure to Environmental Chemicals
Proposal for a social class measure. Working Group of the Spanish Society of Epidemiology and the Spanish Society of Family and Community Medicine
Aten Primaria
Causal inference considerations for endocrine disruptor research in children's health
Annu Rev Public Health
Environmental and occupational interventions for primary prevention of cancer: a cross-sectorial policy framework
Environ Health Perspect
Cited by (24)
Organochlorinated pesticides in Italian women of reproductive age: Serum levels and determinants of exposure
2023, Hygiene and Environmental Health AdvancesReductions in blood concentrations of persistent organic pollutants in the general population of Barcelona from 2006 to 2016
2021, Science of the Total EnvironmentCitation Excerpt :Both in women and men concentrations of OCs (OCPs and PCBs) increased with age, as often reported. The observation probably results from age-cohort-period effects (Porta, 2018; Porta et al., 2008; Porta, 2004; Quinn and Wania, 2012; Gasull et al., 2013). In fact, no compound showed a larger decrease from 2006 to 2016 in the oldest than in the younger groups, whereas for β-HCH, PCBs, naphthalene and phenanthrene the decrease was larger in the younger groups, mostly with monotonic trends.