New research published monthly continues to shed light on the negative health effects of air pollution which include aggravation of existing cardiovascular and respiratory diseases, development of chronic diseases like asthma and heart disease, and even an early risk of death. Traditionally considered to be reserved for severe pollution events, the health concerns surrounding air pollution have been linked to even low levels of air pollution typically considered safe. Questions have begun to arise about the long term consequences of air pollution and how it may affect the incidence of many chronic diseases years down the road. This question was recently addressed using mice by a team of researchers from Harvard.
It has been determined in previous studies that exposure to particulate matter in air pollution during pregnancy can increase the susceptibility of the offspring to developing asthma. This team of researchers set out to understand whether this increased risk for asthma was limited to one generation or was seen across multiple generations even after the initial exposure in the grandmother. To do this, the researchers took pregnant mice and exposed them one time to high levels of air pollution. They then took the offspring and sensitized them to low levels of allergen to see if they were more reactive then their non-pollution exposed counterparts. When they looked in the airways of these mice there was a significant increase the number of eosinophils in the airways. Eosinophils are an important immune cell in the development of asthma and so it was suggested by the authors that this represented an increased risk for asthma like changes. Interestingly, when the grandchildren and great grandchildren were analyzed they also had an increase in the number of eosinophils in the airways if their grand or great grandmother was exposed to air pollution. It appeared that the air pollution was causing changes to the on/off switches of the genome (called epigenetic modification). These types of modifications are known to persist for many generations and are one-way key traits are passed from parent to child.
This paper interesting because it suggests that the damaged caused by air pollution doesn’t only effect the immediate population but could affect numerous unborn children generations down the road. There are some things, however, that you should keep in mind with these results. First, if air pollution increases asthma susceptibility for 3 generations then why doesn’t everyone have asthma? It is likely that the story is much more complicated than this and involves genetics and other exposures early in life. Second, keep in mind that these are mice and that mice don’t actually get asthma. If you stop giving them the allergens their inflammation goes away. This does not occur in humans. Third, the allergen used in this experiment, ovalbumin or egg protein, is good scientifically because it allows precise control of the exposure but it is not useful in the real world. People with asthma are triggered by house dust mites, cat and dog dander, pollen, and cigarette smoke not egg protein. Additionally, the mice need to be made allergic to the ovalbumin since it inherently does not cause a response. With these things in mind this research does give us some clues about the possible long term effects of air pollution and why we must get out current situation under control. This is not a problem that just affects our immediate health but the health of our children to come.
Image Credit: Flickr Billy Wilson