The Cognitive and Behavioral Effects of Lead Exposure
On Friday, November 9, 2018, a Chicago Tribune headline read Firm Cited for Lead in Tainted Indy Areas (Hawthorne, 2018, p. 4). The story discusses the lead contamination in northwest Indiana. It details the role government officials played in allowing this exposure to continuously be a problem throughout the past few years. Now, air quality levels in the area are twice the legal limit according to the standards set by the Environmental Protection Agency. The article refers to lead as a brain-damaging metal that has the capability to permanently damage the developing brains of children (Hawthorne, 2018). This article focuses on the negligence of government officials in attending to the lead exposure problem in this area. However, lead exposure is not limited to one area, and Indiana government officials are not the only ones ignoring a prevalent environmental issue.
Lead exposure is an important national and international issue. Researchers publish new studies each year increasing the knowledge regarding the adverse effects of lead. The Centers for Disease Control (CDC) previously declared certain blood lead levels safe for children and adults. This safe level has continuously been reduced over the years. As Ris, Dietrich, Succop, Berger, & Bornschein (2003) note, in 1970, the blood-lead level of exposure considered dangerous was 60g/dL or higher. In 1971, it became 40g/dL, and in 1978, it decreased to 30g/dL. By 1985, the highest acceptable level was 25g/dL (Ris et. al., 2003). Earlier studies used this benchmark number to determine that adverse effects occur well below this 25g/dL amount (Bellinger, Leviton, Waternuax, Needleman, & Rabinowitz, 1987). More recent studies have continued to find harmful effects of lead exposure at even lower levels. The safe level was reduced to 10g/dL in 1991 (Dietrich, Berger, Succop, Hammond, & Bornschein, 1993). Currently, the CDC declares that there is no safe level of lead exposure, especially in young children (Ris et al., 2003).
Even with more knowledge regarding the effects of lead on young children, lead exposure is still a problem today. As Hanna-Attisha, LaChance, Sadler, and Schnepp (2016) note in their recent study, in Flint, Michigan blood lead levels have been alarmingly high due to exposure through leaded drinking water pipes. This exposure is again the product of governmental negligence, since officials did not conduct proper testing on the drinking water pipes before changing the supply. Hanna-Attisha et al. (2016) conducted a study that examined the level of the lead exposure in Flint. The study analyzed the blood lead levels of children in the area before and after the water source was contaminated. Hanna-Attisha et al. found that blood lead levels significantly increased after the water source change. In addition, they found no significant difference in blood lead levels in children who lived outside the city and most likely did not drink from the city water supply. Overall, the research concluded that elevated blood lead levels (or those above 5g/dL) had significantly increased in Flint-residing children. Blood lead levels at this concentration produce long-lasting adverse behavioral effects and cognitive deficits. Hanna-Attisha et al. portrayed the crisis-level of the situation in Flint by analyzing the blood lead levels confirmed in children living within the city. Perhaps not surprisingly, Hanna-Attisha et al. found the most profound increases in blood lead levels in the lower socioeconomic neighborhoods in Flint (Hanna-Attisha et al., 2016).
Environmental lead exposure is a severe public health concern. While the overall national average exposure levels have been steadily declining, the current levels in certain areas of the country, such as northwest Indiana and Flint, Michigan are particularly alarming. Some areas display hotspots for lead exposure. Fergusson, Fergusson, Horwood, & Kinzett (1988) conducted the first part of a three-part study to examine whether specific environmental factors such as social disadvantage, exposure to old wooden housing, exposure to busy roads, and pica increased risk of lead exposure. All four environmental factors were significantly associated with higher lead levels and this effect remained when each of the factors was considered independently of the other three. These findings indicate that lower socioeconomic status (SES) groups are more at risk for lead exposure. SES is an important consideration when discussing the results of studies on lead exposure and its impact on cognition and behavior. It will be a covariate included in much of the research outlined in this paper.
Lead exposure poses a serious problem in our society today. The effects of early lead exposure can be severe and long-lasting. This paper will focus on the adverse effects of early lead exposure on cognition and behavior. First, it will outline general sources of and outcomes associated with lead exposure, and provide an overview of the impact of lead exposure on brain development, as well as the long-and-short term cognitive deficits and behavioral problems. Next, the paper will turn more specifically to the literature regarding the cognitive effects of lead exposure and the impact of lead on a range of cognitive outcomes in humans and non-human animals. Next, the paper will discuss a range of behavioral effects of lead exposure in non-humans and humans, including hyperactivity, impulsivity, behavioral problems, aggression, and even criminal behavior. Finally, the discussion will integrate the findings from the cognitive and behavioral sections, as well as expand on these findings to address implications of this research, including those involving SES and current policy about lead exposure.