Environmental Engineering Reference
In-Depth Information
typical family consumes in 1 week. The results showed that the average concen-
tration of lead was between 1.1 and 30.7
µ
g/L with a median of 4.8
µ
g/L.
According to Health Canada (
1992
), Graham
'
s
findings translate to an ingestion of
lead of 7.2
g per day for an adult and a 2-year-old child, respectively, if
we assume that an adult consumes 1.5 L and a child consumes 0.6 L of drinking
water per day.
The same Health Canada (
1992
) study showed that (1) drinking water accounts
for 9.8 and 11.3 percent of total lead intake for a child and an adult respectively; (2)
for the remaining sources of lead exposure food, air and dust account for 50.9, 1.2,
and 38 percent respectively for 2-year-old children and 78.0, 7.1, and 4.2 percent
respectively for adults; (3) of the total lead that is absorbed into the bloodstream,
drinking water accounts for 10.7 percent of total lead for adults and 11.6 percent for
a 2-year-old child; (4) of the 2.9
µ
g and 2.9
µ
µ
g of lead ingested per day by a 2-year old,
1.45
g of lead
ingested per day by adults is absorbed; and (5) compared to other sources of lead
exposure, food and water have the highest absorption rate (50 percent) for 2-year-
old children. For children under 2 years of age, in particular bottle-fed infants, the
absorption rate from water used for dietetic purposes is much higher.
In more recent work, Fertmann et al. (
2004
) found signi
µ
g is absorbed into the bloodstream, while only 0.72
µ
g of the 7.2
µ
cant correlation
between BLLs and average lead concentration in tap water after examining BLLs in
over 200 women in Hamburg. They also found that women from households that
had drinking water lead above 5
cantly higher BLLs than those that
had no detectable lead in their drinking water. A follow-up study on a subset of the
group revealed a signi
µ
g /L had signi
cant reduction in BLLs after they were advised either to
flush prior to consuming water or to consume bottled water. Edwards et al. (
2009
)
found strong correlation between lead levels in drinking water and BLLs above
10
g/dL for children under 1.3 years of age. Surprisingly, the correlation between
BLL and drinking water lead was weaker when children up to 2.5 years of age were
included in the study.
The above studies indicate a good correlation between BLLs and drinking water
at the tap. However, changes to water treatment processes prior to distribution to
residential homes can also in
µ
uence blood lead levels. Silico
uorides,
fluosilicic
acid, and sodium
fluoridate over 90 percent of US municipal
water, but have been shown to increase the risk of elevated blood lead (i.e. BLLs
over 10
fluosilicate are used to
g/L) in children by up to 200 percent when compared to children con-
suming non-
μ
uoridated water (Coplan et al.
2007
). Miranda et al. (
2007
) conducted
a study in Wayne County, North Carolina, which showed that when municipal
water authorities switched their disinfection treatment process to chloramine dis-
infection, it might have led to increased BLLs. Levin et al. (
2008
) reviewed the
contribution to BLLs from various sources of lead exposure and found that changes
in water treatment processes by water authorities can in
uence BLLs, and that the
risk of elevated BLLs in children is greater when their homes have lead service
lines.
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