Academic journal article Environmental Health Perspectives

Maternal Peripartum Serum DDT/E and Urinary Pyrethroid Metabolite Concentrations and Child Infections at 2 Years in the VHEMBE Birth Cohort

Academic journal article Environmental Health Perspectives

Maternal Peripartum Serum DDT/E and Urinary Pyrethroid Metabolite Concentrations and Child Infections at 2 Years in the VHEMBE Birth Cohort

Article excerpt

Introduction

To control mosquito vectors, malaria control programs in 85 predominantly low- and middle-income countries apply insecticides directly to the inside walls of homes, a process known as indoor residual spraying (IRS). Consequently, approximately 106 million people may inadvertently become exposed to IRS insecticides (World Health Organization [WHO] 2016). Fetal exposure to insecticide used for IRS, including the pyrethroid deltamethrin and dichlorodiphenyltrichloroethane (DDT) and its breakdown product dichlorodiphenyldichloroethylene (DDE), have been shown in many animal and in vitro studies to alter immune function (Rehana and Rao 1992; Santoni et al. 1998; Banerjee 1999; Misumi et al. 2005; ATSDR 2002, 2003; Brander et al. 2016) and to specifically increase susceptibility to infection (Nunez et al. 2002; Suwanchaichinda et al. 2005; Rehman et al. 2011). However, epidemiologic investigations of associations between fetal insecticide exposure and childhood infections have yielded conflicting evidence.

In a Spanish cohort, maternal antepartum p,p'-DDE blood concentrations were associated with higher risk of lower respiratory tract infection (LRTI) in the first year of life (Sunyer et al. 2010; Gascon et al. 2012). Similarly, in highly exposed Arctic populations, maternal p,p'-DDE concentrations were associated with elevated risks of gastrointestinal, ear (otitis media), and upper respiratory tract infections (URTI) in 1-y-olds (Dewailly et al. 2000; Dallaire et al. 2004), although dose-response trends were only detected with aggregated infections (Dallaire et al. 2004). Other studies have reported associations with lower risk of infections. For example, a German study reported that child (postnatal) p,p'-DDE concentrations were associated with lower risk of otitis media in 7- to 10-y-olds (Karmaus et al. 2001) and a Mexican study observed an association between higher prenatal p,p'-DDE concentration and lower risk of LRTI in 2-y-old boys (Cupul-Uicab et al. 2014). No studies have reported associations with DDT, possibly because of low detection frequencies (Sunyer et al. 2010). To our knowledge, no human studies have investigated associations between fetal pyrethroid exposure and child infections in settings where IRS is conducted.

Individuals living in IRS areas have been shown to have tissue concentrations of these chemicals orders of magnitude higher than in general populations (Gaspar et al. 2017; Aneck-Hahn et al. 2007; Whitworth et al. 2014). Understanding potential adverse side effects of IRS on childhood infections is critical because respiratory and gastrointestinal infections are leading causes of child morbidity and mortality in these settings. In our study area (Limpopo Province, South Africa), intestinal infections, influenza, and pneumonia together account for 26.2% and 23.6% of all deaths among infants under 1 y and children 1-14 y of age, respectively (Statistics South Africa 2017). Moreover, early adversity factors such as poverty (Appleton et al. 2016; Stein et al. 2016), malnutrition (Banerjee 1999; Bourke et al. 2016; Prescott 2016); and HIV (Ruck et al. 2016; Slogrove et al. 2017) are common among pregnant women in this setting and may increase children's susceptibility to any adverse impact of insecticides. This study aims to investigate whether prenatal exposure to IRS-related chemicals is associated with increased incidence of childhood infection and whether potential effects of IRS insecticides may be exacerbated by these susceptibility factors.

Methods

Study Population and Recruitment

The current study was conducted in the context of the Venda Health Examination of Mothers, Babies, and their Environment (VHEMBE), a prospective birth cohort study investigating the effects of environmental exposures on the health and development of children born in the Vhembe district of Limpopo Province, South Africa, where IRS insecticides, primarily DDT and the pyrethroid deltamethrin, are applied during the malarial season. …

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