Environmental Health Criteria 214

HUMAN EXPOSURE ASSESSMENT
Public Health Service's 1962 drinking water standard of 3 pCi/litre.
The time periods 1969-1971 and 1973-1978 were studied for all 28
municipalities in Iowa. After testing each town for radium-226 levels,
the towns were divided into three groups, with respectively 0-2, 2-5
and >5 pCi/litre of radium-226 in the water supply. In towns level
> 5.0 pCi/litre, the incidence of lung and bladder cancer in men and
lung and breast cancers among women was higher (Fig. 47). Although 77%
of the individuals in the study had been on the same water supply for
at least 10 years, misclassification due to uncertainties about past
concentrations and past residential histories create problems for the
study.
A Taiwanese study of a population that used artesian wells
suggests that there may be a link between high arsenic levels in
drinking water and the incidence of internal cancers, particularly
bladder cancer (Chiou et al., 1995). Levels above the maximal
permitted level of 50 µg/litre occur in some locations in the western
USA. In 1978 a study was done in Utah of individuals between the ages
of 21 and 84. Concentrations of arsenic in the water ranged from 0.5
to 160 µg/litre (mean 5.0 µg/litre). Two indexes of exposure were
used, both of them assuming constant past levels in the water supply:
* total cumulative exposure was calculated using the duration of time
spent in the town, the rate of water consumption, and the 1978
levels of arsenic in the drinking-water
* intake concentration was calculated using the above measurements,
as well as the total fluid intake, to approximate the arsenic
concentration in the urine to which the bladder is exposed (Bates
et al., 1995).
Overall, no association between arsenic exposure and bladder
cancer was seen with either index (Table 42). The only odds ratio
(3.32) significantly different from 1 was for smokers with a
cumulative dose greater than 53 mg. This suggests that smoking
potentiates the relationship between arsenic and bladder cancer.
That drinking-water can be a main source of exposure could be
shown in the framework of German Environmental Survey (see Chapter
2.6). Drinking-water (first draw and grab samples, see Chapter 7.3.2)
was analysed in approximately 4000 German households. A significant
correlation was observed between the lead content in drinking water
and the lead content in the blood of the population (Nöllke et al.,
1995; Becker et al., 1997).
12.6 Exposure to microbes
Examination of biological contamination involves a different
approach, as discussed in Chapter 9. Bioaerosol samples are widely
used and rely on impaction on to culture medium. The cut-off size of
the samplers limits the ability to capture all bioaerosols, and no one
culture medium and growth temperature is appropriate for all viable
bacteria in the air. Therefore, the numbers from the impactor will be
less than those actually present in the air because of limited power
of detection. Chemical assay for endotoxin is independent of the
ability to grow the bacteria, but it is sensitive to sampling and
storage procedures.
Previous studies of bioaerosols in the occupational setting have
examined levels of airborne bacteria. A study of bioaerosols at water
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