Relative contribution of potential modes of surface dust lead contamination in the homes of boatyard caulkers.
OBJECTIVE
The aim of this study was to quantify the relative contributions to surface lead contamination of boat-caulkers' houses of three contamination modes, namely "take-home" lead from the caulker, "natural" spatial dispersal from boatyard to household and "redistribution" of accumulated lead-laden dust within the house.


METHODS
Boat-caulkers' houses situated in areas surrounding boat repair yards were recruited. Caulkers' houses that were located close together were divided into location-matched pairs, within which one was randomly assigned to be given a cleaning and designated a CL house, and the other was to be left uncleaned and designated a NCL house. Geographically isolated caulker's houses were randomly assigned to one of the two categories. The nearest non-boatyard worker's house (NB) was additionally recruited for each set. The surface lead loading rate (SLLR), defined as the mass of lead deposited in dust per unit area of surface per unit time, was measured over a period of 3 mo in all houses, and the data were modeled using linear mixed effects regression.


RESULTS
Adjusted values of SLLR differed only slightly between CL and NCL houses (0.96 to 1.02 times) but were between 1.65 and 2.03 times higher in CL and NCL houses than in NB houses depending on proximity to the boatyard and between 2.12 and 2.61 times higher in houses within one km of a boatyard than in more distant houses depending on category of house.


CONCLUSIONS
Newly deposited dust lead likely resulted from the take-home and spatial dispersion modes. The contribution of redistribution is very small.
Bureau of Occupational and Environmental Diseases, Ministry of Public Health, Thailand. untimanon@gmail.com
Orrapan
O
Untimanon
Alan
A
Geater
Virasakdi
V
Chongsuvivatwong
Wiyada
W
Saetia
Pia K
PK
Verkasalo
D000395:Air Pollutants, Occupational; D004391:Dust; D006798:Housing; D006801:Humans; D007854:Lead; D016014:Linear Models; D012767:Ships; D013785:Thailand
D000395:Air Pollutants, Occupational; D004391:Dust; D007854:Lead