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Camila Alexandrina Figueiredo,¹ Neuza Maria Alcântara-Neves,¹ Rafael Veiga,¹ Leila D. Amorim,² Vitor Dattoli,¹ Lívia Ribeiro Mendonça,¹ Samuel Junqueira,¹ Bernd Genser,³ Mariese Santos,² Lain Carlos Pontes de Carvalho,⁴ Philip J. Cooper,⁵ Laura Rodrigues,⁶ and Maurício L. Barreto³

¹Instituto de Ciências da Saúde, ²Instituto de Matemática, and ³Instituto de Saúde Coletiva, Universidade Federal de Bahia, Salvador, Brazil; ⁴Centro de Pesquisas Gonçalo Moniz–FIOCRUZ, Salvador, Brazil; ⁵Universidad San Francisco de Quito, Quito, Ecuador; ⁶London School of Hygiene and Tropical Medicine, London, United Kingdom

Abstract
Background: Environmental factors are likely to have profound effects on the development of host immune responses, with serious implications for infectious diseases and inflammatory disorders such as asthma.

Objective: This study was designed to investigate the effects of environmental exposures on the cytokine profile of children.

Methods: The study involved measurement of T helper (Th) 1 (interferon-gamma) , Th2 [interleukin (IL) -5 and IL-13], and the regulatory cytokine IL-10 in unstimulated peripheral blood leukocytes from 1,376 children 4–11 years of age living in a poor urban area of the tropics. We also assessed the impact of environmental exposures in addition to biological characteristics recorded at the time of blood collection and earlier in childhood (0–3 years before blood collection) .

Results: The proportion of children producing IL-10 was greater among those without access to drinking water [p < 0.05, chi-square test, odds ratio (OR) = 1.67]. The proportion of children producing IL-5 and IL-10 (OR = 10.76) was significantly greater in households that had never had a sewage system (p < 0.05, trend test) .

Conclusions: These data provide evidence for the profound effects of environmental exposures in early life as well as immune homeostasis in later childhood. Decreased hygiene (lack of access to clean drinking water and sanitation) in the first 3 years of life is associated with higher spontaneous IL-10 production up to 8 years later in life.

Key words: age, breast-feeding, cytokine profile, IL-10, SCAALA, sewage, sex, tap water. Environ Health Perspect 117:845–849 (2009) . doi:10.1289/ehp.0800366 available via http://dx.doi.org/ [Online 9 January 2009]

Address correspondence to C.A. Figueiredo, Universidade Federal da Bahia–UFBA, Instituto de Ciências da Saúde, Departamento de Biorregulação, Av. Reitor Miguel Calmon, s/n, Vale do Canela–CEP: 41110-100, Salvador-BA, Brazil. Telephone/fax: 557132838948. E-mail: cavfigueiredo@gmail.com

We thank the individuals who contributed directly or indirectly to this work, including laboratory technicians, fieldworkers, and students. The Brazilian agencies CAPES, CNPQ, and FAPESB are also acknowledged for providing postdoctoral, masters, and doctoral fellowships. We thank M. Yazdanbakhsh for careful reading of the manuscript.

This study was funded by The Wellcome Trust, U.K., and HCPC Latin America Excellence Centre Programme, Ref 072405/Z/03/Z.

The authors declare they have no competing financial interests.

Received 4 November 2008 ; accepted 9 January 2009.