Does Nitrogen Dioxide Cause Asthma in Children?

The Hill — Equilibrium/Stability, an environmental report put out by The Hill, makes the following claims:

The burden of pollution falls particularly hard on children, according to another Lancet study, which found that the pollutant nitrogen dioxide, or NO2 — a common byproduct of burning fossil fuels in cars and power plants ­­– has led to almost 2 million additional cases of childhood asthma.

The link in the quote is to the Medical press and an article by George Washington University which claims after a picture of smokestacks billowing what appears to be horrible pollutants, but may well be nothing but water vapor, especially given the lighting conditions:

Nearly 2 million new cases of pediatric asthma every year may be caused by a traffic-related air pollutant, a problem particularly important in big cities around the world, according to a new study published today. The study is the first to estimate the burden of pediatric asthma cases caused by this pollutant in more than 13,000 cities from Los Angeles to Mumbai.

“Our study found that nitrogen dioxide puts children at risk of developing asthma and the problem is especially acute in urban areas,” Susan Anenberg, a co-lead author of the article and a professor of environmental and occupational health at the George Washington University, said. “The findings suggest that clean air must be a critical part of strategies aimed at keeping children healthy.”

Examining the link in this last quote, we go to the paper in The Lancet entitled Long-term trends in urban NO2 concentrations and associated paediatric asthma incidence: estimates from global datasets.  What do we find here?

NO₂ itself has been associated with adverse health outcomes including asthma exacerbation.  Epidemiological studies have also found associations between transportation-related air pollutants and new onset asthma in children.  Toxicological and gene environment research indicates that transportation-related air pollutants cause airway inflammation and remodelling due to oxidative stress, resulting in asthma development in some individuals.  Epidemiological studies are generally consistent in their finding that NO₂ is significantly associated with paediatric asthma incidence, whereas the evidence for other transportation-related air pollutants (eg, PM_2·5) is more mixed.  Although the putative agent causing asthma in the traffic-related air pollution mixture is unknown, NO₂ could serve as a surrogate for other pollutants causing observed health effects.

I added the bold in each of the above quotes to emphasize the slippery impression that nitrogen dioxide is a cause of childhood asthma.  The first article in The Hill — Equilibrium/Stability implies that it is a cause of childhood asthma.  The second article says it may be a cause in one paragraph and then says it puts children at risk of developing asthma, which means that it is a cause of asthma.  The Lancet paper implies that NO2 is somehow “associated” with asthma exacerbation, but then says that the agent causing asthma in traffic-related air pollution is unknown.  Nonetheless, the gist of the paper is that NO2 causes 2 million additional cases of childhood asthma.

The CDC still says that the cause of childhood asthma is unknown. It says:

While we don’t know what causes asthma, we do know how to prevent asthma attacks or at least make them less severe.

The bottom line is that we do not know that NO2 is causing asthma.  But, the radical environmentalists and the proponents of the failed catastrophic man-made global warming hypothesis very much want to create the impression that this product of carbon-based fuel combustion is poisoning children.  The game is a parallel to the darkening of water vapor emissions from smokestacks to make them look like evil pollutants.  It is like the construction of a case against coal-fired power plants based on their mercury emissions that I blew out of the water years ago on this blog.

There are far too many people politicizing science and, in the process, falsifying science.

On Mercury from coal-fired power plants, see:

Evaluating the Mercury Emissions Danger from Coal-Fired Power Plants