Outdoor and indoor UFP in primary schools across Barcelona

Sci Total Environ. 2014 Sep 15:493:943-53. doi: 10.1016/j.scitotenv.2014.06.072. Epub 2014 Jul 5.

Abstract

Indoor and outdoor measurements of real-time ultrafine particles (UFP; N10-700 in this study) number concentration and average diameter were collected twice at 39 primary schools located in Barcelona (Spain), with classrooms naturally ventilated under warm weather conditions. Simultaneous outdoor N concentration measurements at schools under different traffic exposures showed the important role of this source, with higher levels by 40% on average at schools near heavy traffic, highlighting thus the increased exposure of children due to urban planning decisions. A well-defined spatial pattern of outdoor UFP levels was observed. Midday increases in outdoor N levels mainly attributed to nucleation processes have been recorded both at high and low temperatures in several of the outdoor school sites (increasing levels by 15%-70%). The variation of these increases also followed a characteristic spatial pattern, pointing at schools' location as a key variable in terms of UFP load owing to the important contribution of traffic emissions. Indoor N concentrations were to some extent explained by outdoor N concentrations during school hours, together with average temperatures, related with natural ventilation. Outdoor midday increases were generally mimicked by indoor N concentrations, especially under warm temperatures. At specific cases, indoor concentrations during midday were 30%-40% higher than outdoor. The time scale of these observations evidenced the possible role of: a) secondary particle formation enhanced by indoor precursors or conditions, maybe related with surface chemistry reactions mediated by O3, and/or b) UFP from cooking activities. Significant indoor N increases were detected after school hours, probably associated with cleaning activities, resulting in indoor N concentrations up to 3 times higher than those in outdoor. A wide variability of indoor/outdoor ratios of N concentrations and mean UFP sizes was detected among schools and measurement periods, which seems to be partly associated with climatic conditions and O3 levels, although further research is required.

Keywords: Children's exposure; Cleaning; Ozone; Photochemistry; Traffic-related UFP.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Air Pollutants / analysis*
  • Air Pollution, Indoor / analysis*
  • Environmental Monitoring*
  • Particulate Matter / analysis*
  • Schools*
  • Spain
  • Ventilation

Substances

  • Air Pollutants
  • Particulate Matter