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Pre-natal exposure to air pollution increases risk of ADHD

Children that are born and grow up in poorer, polluted, urban areas may be at greater risk for ADHD, according to a new study.

Pollution exposure had already been linked to ADHD by the Columbia University researchers, but they show in this new study that its negative effects are significantly compounded by the effects of poverty.

The study is the first to substantially demonstrate the link between poverty, exposure to pollution – both in the womb and in childhood – and ADHD. 

The more air pollution a child’s mother was exposed to when she was pregnant, the more likely the child was to have more severe ADHD-related behavior problems later in life.

Pregnant women that live in the stressful conditions of poverty and are exposed to air pollution are more likely to have children with ADHD, a new study finds

The researchers have been studying a group of Dominican and African American women from historically low-income areas of New York City since 1998.

They have kept up with the women since pregnancy, and continue to observe them and  their children.

Data about these women and their children have helped researchers examine the effects of all manner of environmental exposures and factors on childhood development and health.

The researchers took a sample of blood from the pregnant women when they delivered their babies in order to measure an indicator of their exposure to certain toxins that are common in polluted urban air. 

Polycyclic aromatic hydrocarbons (PAH) are toxins in air pollution, commonly produced by combustion processes, such as car exhaust, in high volumes in cities.

Study author Dr Frederica Perera’s suggestions for reducing pollution’s effects 

Air pollution can’t be avoided altogether, but Columbia University researcher Dr Perera says that everyone, and pregnant women especially, should take precautions to protect themselves and their children. 

  • Eat a healthy diet. The nutrients in fruits and vegetables help protect the body against the effects of pollution, as do antioxidants. 
  • Don’t smoke, and avoid smokers. Smoke can also had adverse birth effects, and worsen the effects of pollution. 
  • Keep the air clean at home. Make sure your home is well-ventilated, and void cooking or burning things over an open flame indoors.

If a woman is exposed to these carcinogenic toxins while she is pregnant, they can be absorbed into her bloodstream, passed to her developing baby and cause damage to its DNA and developing brain.

Pollution has been linked to a number of health problems, ranging from lower birth weights, to respiratory problems, and even other problems with the nervous system and behavior.  

Socioeconomic stress is also known to increase the risk of inflammation, and Inflammation of any kind can pose a danger to the rapidly changing fetus’s brain.

So, the researchers posited that the two risk factors together could heighten the risk of worse ADHD symptoms later in a child’s life.

About 11 percent of all children between the ages of four and 17 in the US have been diagnosed with ADHD, but, the study notes, the disorder has multiple ‘complex’ causes. 

The behavioral disorder is thought to be caused in part by genetic predisposition and in part by environmental and social conditions.  

The researchers continued to track the women’s conditions, as well as the behavior of their children, for the next nine years, and found that they were right: poverty and pollution combine to predict ADHD in the nine-year-old children.  

Low-income communities tend to be made up largely of people of color, like those in the study. They also tend to be in urban areas where the air is most polluted, the study notes. 

A robust body of previous research shows that these factors all combine to leave groups like the one the Columbia researchers followed vulnerable to various physiological diseases and disorders.

But, even though these types of studies are ‘the gold standard in epidemiology, they cannot prove causation,’ says Dr Frederica Perera, the study’s lead author. 

This data, though, shows ‘significant associations,’ between pollution, poverty and ADHD that are consistent with other findings on the relationship between either poverty or pollution and childhood development. 

The message to take away from the study, however, is a more nuanced than a simple warning against living and raising children in poorer, urban areas, Dr Perera says. 

‘The fact is that these pollutants are ubiquitous because of our dependence on fossil fuel in all these different forms, and it’s really difficult to escape exposure,’ she says. 

Inevitably, pollutants will permeate homes anywhere, but there are things people – and pregnant women especially – can do to protect themselves, and things policy makers can do to protect people. 

She says that at home, diets that are high in fruits, vegetables and antioxidants can actually help protect the body from the effects of pollution. Secondhand smoke and open burning can exacerbate the effects of pollution, on the other hand, so these should be avoided. 

But ‘ambient air does get indoors, and that’s a policy issue,’ says Dr Perera. ‘With greater awareness by policy-makers and the public, actions can be taken.’ 

She notes that air quality has improved in New York City in the past decade, and that trends show that that effort is paying off. 

The study, Dr Perera says, tells ‘a story about the importance of taking these preventative, protective actions and protecting children in many ways. When we protect them, we protect ourselves.’