Academic journal article Environmental Health Perspectives

Early-Life Exposure to Organophosphate Pesticides and Pediatric Respiratory Symptoms in the CHAMACOS Cohort

Academic journal article Environmental Health Perspectives

Early-Life Exposure to Organophosphate Pesticides and Pediatric Respiratory Symptoms in the CHAMACOS Cohort

Article excerpt


Asthma is the most prevalent pediatric chronic disease [Pijnenburg 2012; World Health Organization (WHO) 2007], and is a leading cause of hospitalization in children (Mellon and Parasuraman 2004) and school absenteeism due to chronic disease (Mellon and Parasuraman 2004). It is estimated that by 2025, > 350 million people globally, mostly children, will have asthma (Pawankar et al. 2011; WHO 2007). Early-life exposures to maternal smoking, secondhand tobacco smoke, and various ambient air pollutants have been linked to respiratory symptoms and disease in childhood (Pawankar et al. 2011; Selgrade et al. 2013; WHO 2007) and adulthood (Stocks and Sonnappa 2013; WHO 2007). The impact of early-life exposures on later respiratory health is biologically plausible: During the first half of gestation, bronchi are developing and airways are branching; during the second half of gestation, alveoli begin to develop; and for several years after birth, the lungs continue to mature with rapid increase in number, size, and complexity of the alveoli (De Luca et al. 2010).

Organophosphate pesticides (OPs) are one of the most commonly used classes of insecticides worldwide. The U.S. Environmental Protection Agency (EPA) phased out most residential use of OP pesticides by the mid-2000s. However, in 2007, 15 million kg of OPs--36% of total insecticide use--were applied in agriculture in the United States (Grube et al. 2011; Guha et al. 2013; U.S. EPA 2013). Widespread OP exposure in the general U.S. population is supported by the frequent detection of diakyl phosphates (DAPs), urinary metabolites of OP pesticides, in the U.S. National Health and Nutrition Examination Survey (NHANES) (Bradman et al. 2005; CDC 2004, 2014).

OPs depress acetylcholinesterase (AChE), allowing acetylcholine to build up in neuronal junctions, including those of the parasympathetic nervous system, which helps modulate control of the airways (Barnes 1986). In animal studies, the OPs--chlorpyrifos, parathion, and diazinon--induced airway hyperreactivity at doses below those causing AChE inhibition (Fryer et al. 2004; Lein and Fryer 2005; Ndlovu et al. 2011; Proskocil et al. 2013). OP exposure has been associated with respiratory symptoms in adults in occupational settings (Hoppin et al. 2006; Kwak et al. 2009; Ndlovu et al. 2011) and in case studies of children following pesticide poisonings (Cavari et al. 2013); however, there have been few investigations of respiratory symptoms following low-level exposure. One nested case-control study (Salam et al. 2004) reported an association between maternal report of exposure to pesticides and herbicides in the first year of life and asthma before 5 years of age. A cross-sectional study of Lebanese children 5-16 years of age (Salameh et al. 2003) reported an association between parental report of para-occupational and residential exposure to pesticides and respiratory symptoms. As noted by others (Kwak et al. 2009; Ndlovu et al. 2011), these studies were based on reported exposure to pesticides, and no studies of children's respiratory health have included biological measures of exposure.

Here we investigate associations between maternally reported respiratory symptoms consistent with possible asthma and pre- and postnatal exposure to OPs, as measured by DAP metabolite concentrations in urine samples collected from pregnant women and their children from an agricultural community in California. We previously reported an association between maternal work in agriculture and increased levels of Th2 (T helper cell) cytokines in these children at age 2 years, which likely play a key role in the pathophysiology of allergic diseases, including childhood asthma (Duramad et al. 2006).


Study setting and design. The Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) study is a longitudinal birth cohort investigating the effects of in utero and postnatal environmental exposures on growth, neurodevelopment, and respiratory disease in residents of the Salinas Valley, California (Eskenazi et al. …

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