Indoor-outdoor Relationships of Carcinogenic Polycyclic Aromatic Hydrocarbons in Portuguese Preschools

Children represent one of the most vulnerable groups in society. The detailed characterization of pollution (both indoors and outdoors) of schools is of great importance, since it may allow preventing potential risks to children health. Yet the information related to carcinogenic compounds, such as some polycyclic aromatic hydrocarbons (PAHs) in child educational settings is very limited. Thus the aim of this work was to assess indoor and outdoor levels of PAHs at Portuguese preschools (3–5 years old children) in urban areas with emphasis on carcinogenic compounds, and to identify the main sources of indoor PAHs. Eighteen PAHs (16 considered by USEPA as priority pollutants, and dibenzo[a,l]pyrene and benzo[j]fluoranthene, the latter recommend EU Directive 2008/50/EC) were collected during 45 days of spring 2013 at two preschools (PS1, PS2) situated in two different (and distant from each other) urban areas in north of Portugal. Nine carcinogenic PAHs were included: benzo[a]pyrene (known carcinogen) and other 8 probable (benz[a]anthracene, dibenz[a,h]anthracene, dibenzo[a,l]pyrene) or possible (naphthalene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene and indeno[1,2,3-c,d]pyrene) carcinogens. PAHs in PM2.5 (particulate matter with aerodynamic diameter < 2.5 m) were simultaneously collected both indoors (classroom, playrooms) and outdoors (playground and preschool yards). Quantification of PAHs was performed by microwave-assisted extraction combined with liquid chromatography with fluorescence and photodiode array detection. Total levels of 18 PAHs (ΣPAHs) were 2.6 and 3.2 higher in indoor and outdoor air of PS1 than at PS2. Compositional profiles were though similar at both preschools with 5–6 ring PAHs being the most abundant. Dibenz[a,h]anthracene and benzo[b]fluoranthene (both class 2A carcinogens) were the predominant individual PAHs at both preschools. Nine carcinogenic compounds (ΣPAHscarc) accounted for 73 and 74% of indoor particulate PAH content at PS1 and PS2, respectively; outdoors the corresponding ΣPAHscarc composed 66% and 71% of ΣPAHs. Analysis of I/O ratios of ΣPAHscarc suggested that outdoor emissions were a significant contributor to indoor carcinogenic PAHs at both schools. ΣPAHscarc exceeded the recommended EU guideline value of 1 ng m (100% of days at PS1, both indoors and outdoors; >65% samples at PS2) for the total content in PM10 averaged over a calendar year. Therefore, in order to prevent risks to children health it necessary to establish and implement target values of carcinogenic components in indoor particles of smaller sizes (i.e. PM2.5).