Ž . The Science of the Total Environment 224 1998 6980 Seasonal deposition of housedusts onto household surfaces Rufus D. Edwards a,  , Edward J. Yurkow b , Paul J. Lioy c a Joint Graduate Program in Exposure Measurement and Assessment, Rutgers Uni  ersity and The Uni  ersity of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, New Brunswick, NJ 08854, USA b ( ) Toxicology Di  ision, En ironmental and Occupational Health Sciences Institute EOHSI , Rutgers Uni  ersity and the Uni  ersity of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA c ( ) Exposure Measurement and Assessment Di  ision, En ironmental and Occupational Health Sciences Institute EOHSI , Rutgers Uni  ersity and the Uni  ersity of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA Received 20 February 1998; accepted 8 September 1998 Abstract Seasonal differences in the particle size fractions and mass loadings of household dust deposited on indoor surfaces were examined in four New Jersey homes. Housedust was collected during a 30-day period on non-electro- static polyethylene sample plates on which a glass slide had been placed. In each home two samples were collected at a height of 1.5 m and two were collected at a height of 0.3 m above the floor. Dust samples were obtained from each home during a summer and winter collection period. Particle size measurement was completed using an adaptation of a Meridian ACAS 570 Interactive Laser Cytometer. Results indicated that the dust mass deposited on household surfaces during the summer was greater than during the winter. The arithmetic mean mass deposition rate for all houses was 0.37 0.13 gcm 2 day during the summer and 0.22 0.13 gcm 2 day during the winter. The total number of particles deposited, however, was greater during the winter than during the summer. The increase in winter time particle number was caused by greater numbers of particles with an equivalent spherical diameter 2.5 m. The most probable source of these particles was winter time combustion emissions within the residences and the subsequent particle deposition on household surfaces. The greater mass loadings measured on the low sampling plates during the summer were associated with a greater number of particles with an equivalent spherical diameter 5 m. In the winter, however, the particle mass and number loadings were similar at both heights. These results suggested that ventilation of the house during the summer allowed resuspended particles to enter which led to the higher levels of settled dust. Measurement of contaminant levels in housedust for exposure estimation therefore, should account for the seasonal and height differences in dust mass, and collect representative fractions of housedust  Corresponding author. EOHSI, Room 360, 170 Frelinghuysen Rd, Piscataway, NJ 08854, USA. Tel.: 1 732 4450162; fax: 1 732 4450116; e-mail: nyika@eohsi.rutgers.edu 0048-969798$ - see front matter  1998 Elsevier Science B.V. All rights reserved. Ž . PII S0048-9697 98 00348-9