Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
concentration was greater than the exposure limit of 30 ng/m 3 at some
of the plants. Bacterial levels were between 10 and 10 5 CFU/m 3
(Table 43).
Sixteen male workers with a mean exposure duration of 10 years
were examined for symptoms related to exposure to bacteria and
endotoxin. The workers' occupational history and symptoms were
evaluated using written questionnaires. Symptoms were found in
6 workers; 4 reported fever, shivering and eye irritation, and 3 a
cough. Although the number of subjects was too low for epidemiological
conclusions based on the symptoms, the levels in some locations were
high. Excessive levels of contamination were restricted to certain
areas of the plant, suggesting that exposure levels should be
minimized by changing the physical layout of those work areas and
improving hygienic practices by individuals after working in those
locations.
Previous work has established that both settled and airborne
house dust contains allergens such as dust mites, animal dander, and
fungi. The connection between home dampness, fungus levels and
respiratory symptoms was investigated in 60 homes as part of a
Netherlands case-control study (Verhoeff et al., 1994b). A
relationship between dust levels and exposure to moulds was
hypothesized, as was a relationship between characteristics of homes
(e.g., dampness and type of flooring).
The level of viable fungal propagules present in settled dust was
chosen as the sampling parameter; dust was collected from the floor
and mattresses using a vacuum cleaner with a cellulose fibre filter.
The presence and number of fungal propagules was determined by plating
the dust on to agar growth medium. A checklist and a questionnaire on
the residence type and occupant behaviour were filled out for each
home.
The geometric mean of the number of dust sampled from the floor
was 8990 CFU/g and it was significantly higher in samples from
carpeted floors (12 880 CFU/g) than from smooth floors (3550 CFU/g).
The level from mattresses was 7660 CFU/g. In rooms where damp spots
Page 228 of 284
Table 43. Concentrations of endotoxin and bacteria (Laitinen et al., 1994)
Phase Endotoxin Gram-negative bacteria
(ng/m 3 ) (10 3 CFU/m 3 )
AM MD Range AM MD Range
Wastewater pumping 16 18