Sex differences in the association between exposure to indoor particulate matter and cognitive control among children (age 6–14 years) living near coal-fired power plants

Highlights

• The association between indoor PM₁₀ concentrations and children's performance on two tests of cognitive control was assessed.

• Higher PM₁₀ concentrations were associated with higher risk of commission errors on tests of cognitive control.

• Females may be more susceptible to impulsivity associated with PM₁₀ exposure.

Abstract

Coal fly ash consists of inhalable particulate matter with varying concentrations of neurotoxic metals. Children living near coal-fired power plants with coal fly ash storage facilities may be exposed to coal fly ash when it escapes as fugitive dust emissions into surrounding communities. Previous research on outdoor particulate matter air pollution of similar aerodynamic diameter (PM₁₀) suggests exposure may be associated with impaired cognitive control. The purpose of this research was to investigate sex-differences in the association between exposure to indoor PM₁₀ and cognitive control among children (n = 221), ages 6–14 years, living near coal-fired power plants with fly ash storage facilities. In an ongoing community-based study, we measured indoor PM₁₀ concentrations in participants' housing units and used performance measures from the BARS (Behavior Assessment and Research System) Continuous Performance Test (CPT) and Selective Attention Test (SAT) to assess neurotoxic effects on cognitive control. In adjusted negative binomial regression models, we found children living in housing units with higher indoor PM₁₀ concentrations had a higher risk of commission errors on the CPT (incidence rate ratio (IRR) = 1.22 per interquartile range difference (IQR = 0.72 μg/m³) in natural log-transformed PM₁₀ concentrations; 95% CI = 1.01, 1.46) and SAT (IRR = 1.14; 95% CI = 1.01, 1.28). Furthermore, child sex modified the association between PM₁₀ concentration and CPT commission errors. Among females, higher PM₁₀ concentration was associated with higher risk of CPT commission errors (IRR = 1.39; 95% CI = 1.06, 1.82), but we found no association among males (IRR = 1.01; 95% CI = 0.79, 1.30). We found no association between PM₁₀ concentrations and CPT or SAT response latency. Our results suggest females living near coal-fired plants with coal fly ash storage facilities may be more susceptible to impaired cognitive control associated with particulate matter exposure. Children living near coal-fired power plants with coal fly ash storage facilities who are exposed to particulate matter may have an increased risk of impulse control problems.

Introduction

When coal is burned to generate electricity, it produces a waste by-product known as coal ash. A major component of coal ash is fly ash, which consists of inhalable particulate matter ranging in diameter from 0.1 μm to >10 μm (Bednar et al., 2013; Brown et al., 2011; Jones et al., 2012; Patra et al., 2012). The production and storage of coal ash is a growing environmental issue and public health concern in communities across the United States. According to the American Coal Ash Association (ACAA), in 2017, coal-fired power plants generated over 111 million tons of coal ash, much of which is stored in open-air landfills and surface impoundments across 47 states (American Coal Ash Association, 2019; U.S. Environmental Protection Agency, 2015 (EPA)). Current coal ash storage methods expose surrounding communities to particles which escape as fugitive dust emissions (Mueller et al., 2013). Although the EPA estimates that 6 million people, including 1.5 million children, are exposed to coal ash (U.S. Environmental Protection Agency, 2015), that number may be higher due to unknown storage facilities and lack of research on coal ash exposure.

The effect of chronic fly ash inhalation on children's health has not been extensively studied. However, research suggests exposure to air pollution particulate matter of similar size can adversely impact childhood neurodevelopment and neuropsychological functioning (Saenen et al., 2016; Suades-González et al., 2015; Sunyer et al., 2015). Particulate matter generated during coal combustion may be particularly harmful for children's development because fly ash particles have been found to contain radioactive elements and varying concentrations of neurotoxic metals, such as manganese, aluminum, and lead (Bednar et al., 2013; Flues et al., 2002; Hatori et al., 2010; Spencer and Drake, 1987). Thus, inhalable fly ash particles, which are capable of penetrating deep into the lungs and entering the bloodstream, may also act as vehicles for neurotoxic metals to enter the bloodstream.

During late childhood and adolescence, the prefrontal cortex is still-developing and susceptible to neurotoxins. If exposure to particulate matter containing metals disrupts development of the prefrontal cortex, then it could cause functional deficits in cognitive control and executive function resulting in impaired self-regulation (Arnsten, 2009; Arnsten and Rubia, 2012). Neurotoxic exposures disrupting brain development can have profound impacts on neuropsychological functioning but may not result in behaviors that reach diagnostic criteria for any specific disorder. For this reason, it is important to assess subclinical impacts of environmental exposure on measures of cognitive control, such as attention and impulse control (Rauh and Margolis, 2016).

In this analysis, we used two tests, the Continuous Performance Test (CPT) and Selective Attention Test (SAT) from the Behavioral Assessment and Research System (BARS) to assess neurotoxic effects on cognitive control among children living near two coal-fired power plants with coal ash storage facilities. Because fly ash particles may be <10 μm in diameter (PM₁₀), we quantified indoor concentrations of PM₁₀ and evaluated the relationship of these concentrations with CPT and SAT performance measures. We hypothesized that children living near the coal-fired power plants with coal ash storage facilities with higher concentrations of indoor PM₁₀ would commit more errors and have longer response times.