3.1.1 Changes in Environmental Exposure
National lockdowns aimed to limit social interactions. In parallel,
restraining the population indoors decreased exposure to environmental
stressors such as respiratory infections, airborne allergens,
particulate matter (PM10, PM2.5) and
other air pollutants.17,18 These stressors are
well-established inducers of airway inflammation, asthma exacerbations
and worsening disease control.19-22 Consistent reports
from across different countries documented decreased physical activity
of children during lockdowns and increased time spent in front of
screens, as a result of the increased time spent
indoors.23-25 One study, using wearable sensors,
objectively measured time spent outdoors and levels of physical activity
in asthmatic children before and during lockdown periods and also
confirmed a marked reduction of both during lockdown.8
Besides decreased outdoor exposure, there was also a notable decrease in
anthropogenic pollutants emissions during lockdowns as a result of the
reduced traffic volume and economic activity, which reversed following
the lifting of the restriction measures.26 Greenhouse
gases, specifically nitrogen dioxide (NO2), carbon
monoxide (CO) and emissions of PM10,
PM2.5 were substantially decreased compared to previous
years.26-28 NO2 reductions were
consistently low compared to non-lockdown periods across European
countries, while levels of PMs were reduced but at different levels,
possibly due to their source variability, such as the natural origin
particulate matter from environmental dusts.29 Few
studies showed no significant decreases in area-specific
PM2.5, PM10, NO2 and
ground-level ozone, despite reporting dramatic reductions in vehicular
traffic, implying that possible reductions in pollutants were not
adequately measured.13