Indoor air quality in nurseries is an interesting case of study mainly due to children’s high vulnerability
to exposure to air pollution (with special attention to younger ones), and because nursery is the public
environment where young children spend most of their time. Particulate matter (PM) constitutes one of
the air pollutants with greater interest. In fact, it can cause acute effects on children’s health, as well as
may contribute to the prevalence of chronic respiratory diseases like asthma. Thus, the main objectives of
this study were: i) to evaluate indoor concentrations of particulate matter (PM1, PM2.5, PM10 and PMTotal)
on different indoor microenvironments in urban nurseries of Porto city; and ii) to analyse those concentrations
according to guidelines and references for indoor air quality and children’s health. Indoor PM
measurements were performed in several class and lunch rooms in three nurseries on weekdays and
weekends. Outdoor PM10 concentrations were also obtained to determine I/O ratios. PM concentrations
were often found high in the studied classrooms, especially for the finer fractions, reaching maxima
hourly mean concentrations of 145 mg m3 for PM1 and 158 mg m3 PM2.5, being often above the limits
recommended by WHO, reaching 80% of exceedances for PM2.5, which is concerning in terms of exposure
effects on children’s health. Mean I/O ratios were always above 1 and most times above 2 showing that
indoor sources (re-suspension phenomena due to children’s activities, cleaning and cooking) were
clearly the main contributors to indoor PM concentrations when compared with the outdoor influence.
Though, poor ventilation to outdoors in classrooms affected indoor air quality by increasing the PM
accumulation. So, enhancing air renovation rate and performing cleaning activities after the occupancy
period could be good practices to reduce PM indoor air concentrations in nurseries and, consequently, to
improve children’s health and welfare.