Neurodevelopmental Disorders and Environmental Toxicants: Epigenetics as an Underlying Mechanism

Abstract

The increasing prevalence of neurodevelopmental disorders, especially autism spectrum disorders (ASD) and attention deficit hyperactivity disorder (ADHD), calls for more research into the identification of etiologic and risk factors. The Developmental Origin of Health and Disease (DOHaD) hypothesizes that the environment during fetal and childhood development affects the risk for many chronic diseases in later stages of life, including neurodevelopmental disorders. Epigenetics, a term describing mechanisms that cause changes in the chromosome state without affecting DNA sequences, is suggested to be the underlying mechanism, according to the DOHaD hypothesis. Moreover, many neurodevelopmental disorders are also related to epigenetic abnormalities. Experimental and epidemiological studies suggest that exposure to prenatal environmental toxicants is associated with neurodevelopmental disorders. In addition, there is also evidence that environmental toxicants can result in epigenetic alterations, notably DNA methylation. In this review, we first focus on the relationship between neurodevelopmental disorders and environmental toxicants, in particular maternal smoking, plastic-derived chemicals (bisphenol A and phthalates), persistent organic pollutants, and heavy metals. We then review studies showing the epigenetic effects of those environmental factors in humans that may affect normal neurodevelopment.

Blood screening for heavy metals and organic pollutants in cancer patients exposed to toxic waste in southern Italy: A pilot study

“…POPs were largely used in the industry, and, despite the ban on their use by the Stockholm Convention on Persistent Organic Pollutants in 2001, they can still be released into the environment mainly owing to the industrial emission or incineration of municipal and industrial waste (Esposito et al, ; Hung, Katsoyiannis, & Guardans, ; Trivedi & Majumdar, ). The World Health Organization (WHO) raised awareness about POP impact on environment and human health, thus encouraging several studies, which demonstrated the association of the exposure to these compounds with cancer development, reproductive problems, neurobehavioral disorders, abnormalities in fetal development, immune alteration, and disruption of hormones (Darras, ; Gregoraszczuk & Ptak, ; Hardell, Bavel, Lindstrom, Eriksson, & Carlberg, ; Lim et al, ; Tran & Miyake, ).…”

“…So, overall, increasing evidence has demonstrated that metals can act as carcinogens through different mechanisms. encouraging several studies, which demonstrated the association of the exposure to these compounds with cancer development, reproductive problems, neurobehavioral disorders, abnormalities in fetal development, immune alteration, and disruption of hormones (Darras, 2008;Gregoraszczuk & Ptak, 2013;Hardell, Bavel, Lindstrom, Eriksson, & Carlberg, 2006;Lim et al, 2017;Tran & Miyake, 2017).…”

Genetics and epigenetics of autism: A Review

“…The mechanism of epigenetic changes that could lead to problems in early fetal brain development has been proposed . Environmental toxins or toxicants, such as those present in pollutants, cigarette smoke, heavy metal, drugs, and plastics, during fetal and childhood development or infection in a mouse model system have been shown to lead to abnormal DNA modifications .…”

“…53 has been proposed. 54 Environmental toxins or toxicants, such as those present in pollutants, cigarette smoke, heavy metal, drugs, [55][56][57] and plastics, during fetal and childhood development or infection in a mouse model system 58 have been shown to lead to abnormal DNA modifications. 22,59,60 The study of epigenetics is more complicated than that of genetics because epigenetics of any tissue could change over time and varies with different tissues collected for the study.…”

The association between particulate matter 2.5 exposure and children with autism spectrum disorder

“…A previous study showed that the etiology of ASD may involve, at least in a subset of children, complex interactions between genetic factors and certain environmental toxicants that may act synergistically or in parallel during critical periods of neurodevelopment, in a manner that increases the likelihood of developing ASD (Rossignol et al, 2014). Another study found the epigenetic effects of environmental factors in humans that may affect normal neurodevelopment (Tran and Miyake, 2017). Environmental chemical exposure may contribute to increased autism prevalence (Sealey et al, 2016).…”