Ultrafine Particles: Exposure and Source Apportionment in 56 Danish Homes

Research output: Contribution to journalArticle


ABSTRACT: Particle number (PN) concentrations (10−300 nm in
size) were continuously measured over a period of ∼45 h in 56
residences of nonsmokers in Copenhagen, Denmark. The highest
concentrations were measured when occupants were present and
awake (geometric mean, GM: 22.3 × 103 cm−3), the lowest when the
homes were vacant (GM: 6.1 × 103 cm−3) or the occupants were
asleep (GM: 5.1 × 103 cm−3). Diary entries regarding occupancy and
particle related activities were used to identify source events and
apportion the daily integrated exposure among sources. Source
events clearly resulted in increased PN concentrations and decreased
average particle diameter. For a given event, elevated particle
concentrations persisted for several hours after the emission of fresh
particles ceased. The residential daily integrated PN exposure in the
56 homes ranged between 37 × 103 and 6.0 × 106 particles per cm3·h/day (GM: 3.3 × 105 cm−3·h/day). On average, ∼90% of
this exposure occurred outside of the period from midnight to 6 a.m. Source events, especially candle burning, cooking, toasting,
and unknown activities, were responsible on average for ∼65% of the residential integrated exposure (51% without the unknown
activities). Candle burning occurred in half of the homes where, on average, it was responsible for almost 60% of the integrated


  • Gabriel Bekö
  • Charles J. Weschler
  • Aneta Wierzbicka
  • Dorina Gabriela Karotki
  • Jørn Toftum
  • Steffen Loft
  • Geo Clausen
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Production Engineering, Human Work Science and Ergonomics
Original languageEnglish
Pages (from-to)10240-10248
JournalEnvironmental Science & Technology
Issue number18
Publication statusPublished - 2013
Publication categoryResearch