An analysis of epidemiological data from the Tarragona region of Spain found that higher prenatal exposure to air pollution was associated with more teacher-reported symptoms of attention-deficit hyperactivity disorder in school-age children. This pollution included particulate matter of various sizes and nitrogen gas. Researchers found no association between exposure to air pollution and the likelihood of receiving a formal diagnosis of the disorder. The paper is Research on psychopathology in children and adolescents.
Air pollution is the presence of harmful particles, gases, and other substances in the air in concentrations that can harm human health and the environment. These particles can take several different forms. For example, some particulate matter is less than 10 micrometers in diameter and is easily inhaled into the respiratory system. Coarse particles typically come from natural sources such as road dust, construction, agriculture, tire and brake wear, soil and pollen.
Unlike particulate matter, nitrogen dioxide is a gas rather than a particle. It is usually produced by combustion processes, especially exhaust gases from automobiles, power plants, and heating systems. Nitrogen oxides are a broad group of reactive gases that primarily include nitric oxide and nitrogen dioxide. Exposure to these particles and gases can irritate the airways and are associated with respiratory and cardiovascular health problems.
Study author Sharanpreet Kaur and colleagues investigated the association between prenatal exposure to air pollutants and attention-deficit hyperactivity disorder in schoolchildren in Tarragona, Spain. Tarragona is a Mediterranean region with a lot of petrochemical activity. It is one of the largest chemical and petrochemical clusters in southern Europe, accounting for about a quarter of the country’s chemical production.
The study authors hypothesized that high prenatal exposure to multiple air pollutants increases the risk of attention-related symptoms in children. They expected that exposure to air pollutants would show stronger associations with general symptoms than formal clinical diagnoses. The researchers also predicted that these associations would be stronger for boys than for girls.
The research team analyzed data from a large epidemiology project tracking neurodevelopmental disorders in Tarragona. In the first phase of the study, families of 3,727 children agreed to participate in screening for attention problems. The children were divided into two age groups, some in preschool and others in late elementary school.
A subset of 781 children participated in the secondary clinical screening phase. The researchers excluded children diagnosed with autism to ensure the data focused only on attention disorders. In this last group, 174 children were formally diagnosed with attention-deficit/hyperactivity disorder, while 549 children were confirmed not to have the condition.
The authors assessed maternal exposure to air pollutants during pregnancy by asking parents about their residential history. They combined this information with data that estimated exposure to traffic-related air pollutants at specific home addresses. This allowed the researchers to estimate the mother’s exposure to various air pollutants during each trimester of pregnancy.
The results showed that higher prenatal exposure to particulate matter and nitrogen gas was associated with increased teacher-reported attention symptoms in a group of school-aged children. However, the data revealed no association between prenatal exposure to air pollutants and the likelihood of a formal diagnosis of symptoms of the disease.
Focusing on specific stages of pregnancy, results showed that exposure to air pollutants during early pregnancy was associated with increased inattention symptoms. Exposure to particulate matter and nitrogen gas during the first two trimesters of pregnancy was found to increase inattention as the child grows older. This association was significantly stronger for boys than for girls.
“Our findings suggest that even small increases in ADHD symptoms may reflect subtle neurodevelopmental effects of prenatal air pollution exposure,” the study authors concluded. “These results highlight that early pregnancy is a vulnerable period and that further research is needed into long-term effects.”
This study contributes to the scientific understanding of environmental risk factors for neurodevelopmental disorders. However, it should be noted that the association between exposure to air pollution and symptom severity is modest. Furthermore, the observational design of this study does not allow direct causal conclusions to be drawn from the results.
The paper, “Prenatal exposure to air pollution and the risk of attention-deficit/hyperactivity disorder in children,” was authored by Sharanpreet Kaur, Josefa Canals-Sans, Paula Morales-Hidalgo, Mònica Guxens, Sami Petricola, and Victoria Arija.
