Secondhand Smoke Exposure and Low Blood Lead Levels in Association With Attention-Deficit Hyperactivity Disorder and Its Symptom Domain in Children: A Community-Based Case–Control Study

Abstract

Aim:Secondhand smoke (SHS) is a major indoor pollutant. We examined the possible association between exposure to both SHS and low levels of lead and attention-deficit–hyperactivity disorder (ADHD) and its symptom domain in children.Methods:This case–control study was based on the results of a community survey using the ADHD rating scale conducted in 49 elementary schools. Both cases and control subjects were confirmed by a child psychiatrist. Each case was matched with one control subject according to gender, school, and grade in school. Using a multivariate conditional logistic regression model, we analyzed 214 case–control pairs of children who ranged in age from 6 to 10 years. Urine and blood levels of cotinine and of lead were determined, and information pertaining to SHS exposure was obtained by means of a questionnaire.Results:Exposure to low levels of lead (geometric mean = 1.65 µg/dL) was related to ADHD, particularly inattention (odds ratio [OR] = 1.67, 95% confidence interval [CI] = 1.07–2.59), whereas SHS exposure was associated mainly with hyperactivity/impulsivity (OR = 3.85, 95% CI = 1.55–9.56). In the pathway from blood lead to hyperactivity/impulsivity, children’s SHS exposure mediated and indirectly accounted for about 73% of this relationship. The combined exposure to lead and SHS synergistically increased the risk of ADHD, evident as both inattention and hyperactivity/impulsivity.Conclusion:SHS, which is associated with hyperactivity/impulsivity in particular, combined with exposure to low blood levels of lead synergistically increased the risk of ADHD. Therefore, the exposure of children to both SHS and lead needs to be reduced.Implications:Although exposure to low levels of lead has been shown to be associated with ADHD, there is little evidence of symptom domain specificity. In our study, low blood lead levels were related to inattention. In addition, prenatal or postnatal exposure to SHS increased the risk of ADHD, particularly hyperactivity/impulsivity. Combined exposure to lead and SHS synergistically increased the risk for both these ADHD symptom domains. To protect children from environmental risk factors related to ADHD, it is necessary to further reduce children’s exposure to SHS and lead, even in those with low blood lead levels.

Passive Smoking Increases Exposure to Polycyclic Aromatic Hydrocarbons and Leads to Prolonged Lipid Oxidation: Lessons From a Natural Experiment in Travelers From Los Angeles to Beijing

“…The concentrations of urinary cotinine in Los Angeles and Beijing in this study were in the same magnitude of other nonsmoking population studies from 20 countries (Table S4) (20,(33)(34)(35)(36). Thus, the level of urinary cotinine in Los Angeles (LA-before + LA-after) was at lower levels compared with that in studies from other countries (Table S4) (20).…”

“…In contrast, urinary cotinine in Beijing was at a relatively higher levels, and it was comparable with levels in studies from Korea and several Europe countries (e.g. Portugal and Hungry) (20,35) but markedly lower that the levels in an Italian Study (36). It is likely that the higher urinary cotinine concentration observed in Beijing was due to a higher prevalence of smoking (30.2%) (37) as compared with Los Angeles (14.3%) (38), together with the markedly higher population density in Beijing (4,700 persons km − 2 ) as compared to that in Los Angeles (2,300 persons km − 2 ) (39).…”

Maternal Smoking and Attention-Deficit/Hyperactivity Disorder in Offspring: A Meta-analysis

“…Fourth, Gard et al 53 reported that girls prenatally exposed to nicotine had greater hyperactivity and/or impulsivity symptoms. Joo et al 54 also found that prenatal secondhand smoke exposure increased the risk of ADHD, especially in terms of hyperactivity and/or impulsivity. It seems that prenatal smoking and/or nicotine exposure may be more relevant to the hyperactivity components of ADHD.…”

A Systematic Review and Meta-Analysis Investigating the Relationship between Exposures to Chemical and Non-Chemical Stressors during Prenatal Development and Childhood Externalizing Behaviors

“…The cigarette smoke data were composed of 21 studies that included a total of 58 sampling events with measurements of prenatal exposures to smoke determined by maternal survey data [16,[75][76][77][78][79][80][81][82][83][84][85][86][87][88][89][90][91][92][93][94]. Four of these studies included exposure data that were specific to the first trimester and included 14 sampling events [80,84,88,94].…”