**3.10 Outdoor air pollution**

There are several groups of air pollutants which are ozone, particulate matter as previously discussed, sulfur dioxide, nitrogen dioxide, carbon monoxide and lead

*Environmental and Occupational Factors; Contribution and Perspectives on Difficult to Treat… DOI: http://dx.doi.org/10.5772/intechopen.108605*


#### **Figure 7.**

*Environmental triggers of asthma.*

respectively. There are multiple environmental triggers of asthma (**Figure 7**). Its Ozone the most recognized factor linked to asthma exacerbations, as well the cause of triggering asthma symptoms. Ozone forms in the air it's not visible, it cannot be smell or taste neither, but it can have strong health impact aggravating asthma symptoms, subsequently increasing use of medications, as well admissions to the hospital due to respiratory conditions. Ozone can be worse in patients with asthma, by which they will be more responsive to inflammation [38]. There are several studies comparing ambient ozone concentrations with increased asthma symptoms, as well risk of hospitalizations and decompensation. There is a positive correlation between severity of asthma and risk of ozone related effects. Traffic related pollutants are part of outdoor environmental factors as well diesel exhaust combustions.
