Prenatal chemical exposures and child language development

Abstract

The goal of this review is to summarize the evidence that prenatal and/or early postnatal exposure to certain chemicals, both man made (insulating materials, flame retardants, pesticides) and naturally occurring (e.g. lead, mercury), may be associated with delays or impairments in language development. We focus primarily on a subset of more extensively studied chemicals—polychlorinated biphenyls (PCBs), lead, and methyl mercury—for which a reasonable body of literature on neurodevelopmental outcomes is available. We also briefly summarize the smaller body of evidence for other chemicals including polybrominated diphenyl ether flame retardants (PBDEs) and organophosphate pesticides. Very few studies have used specific assessments of language development and function. Therefore, we included discussion of aspects of cognitive development such as overall intellectual functioning and verbal abilities that rely on language, as well as aspects of cognition such as verbal and auditory working memory that are critical underpinnings of language development. A high percentage of prospective birth cohort studies of PCBs, lead and mercury have reported exposure-related reductions in overall IQ and/or verbal IQ that persist into middle or late childhood. Given these findings, it is important that clinicians and researchers in communication sciences and disorders are aware of the potential for environmental chemicals to impact language development.

Prenatal PBDE and PCB Exposures and Reading, Cognition, and Externalizing Behavior in Children

“…In their study, Chen A et al (2014) reported that prenatal exposure to PBDEs was associated with cognitive deficits and hyperactivity behaviors in children at age 5 years. However, few studies have assessed the influence of those chemicals on specific cognitive domains, in particular, language development and reading skills (Dzwilewski and Schantz 2015). The prenatal period is the most sensitive time window to the influence of environmental factors on cognitive development, when brain development involves neuronal proliferation, differentiation, and migration (Kang et al 2011; Stiles and Jernigan 2010).…”

Epigenetic impacts of endocrine disruptors in the brain

“…In the rat brain, PCBs alter sexual differentiation of the AVPV and mPOA (Dickerson et al, 2011a; Dickerson et al, 2011b), reproductive senescence [aging; (Walker et al, 2013)], behavior [(Steinberg et al, 2007; Reilly et al, 2015; Bell et al, 2016b); reviewed in (Walker and Gore, 2007)] and cognition [(Widholm et al, 2001); Reviewed in (Schantz and Widholm, 2001; Boucher et al, 2009; Dzwilewski and Schantz, 2015)], outcomes that are influenced by changes in DNA methylation. Additionally, there is some evidence that perinatal exposure to PCBs altered expression of the methylation enzymes, DNMT1 and DNMT3a.…”

Educating speech-language pathologists working in early intervention on environmental health

“…This study suggests that parents and health care providers should be aware of common environmental exposures and how to prevent them, especially given their relationship to developmental delays. A review by Dzwilewski and Schantz suggests that these overall reductions in intellectual function likely hinder language development as well; therefore, it is important for clinicians and researchers in communication sciences and disorders to be aware of these findings [ 9 ].…”