Environmental Engineering Reference
In-Depth Information
Canada (
1992
) indicates a 10.7 percent contribution to lead exposure from drinking
water in Canadian adults, while the USEPA (
1993
) estimates the exposure to the
general population of the US to be between 10 to 20 percent. Regardless of the
relative exposure, drinking water is still one of the largest controllable sources of
lead exposure. Lanphear et al. (
1998
) suggested that leaded water contributed
signi
cantly toward BLLs in children after adjusting for other sources of lead
exposure. Young children are particularly affected due to the ease of absorption of
lead into the bloodstream. Children at 24 months can have a lead uptake of up to
50 percent of the lead they ingest (Health Canada
1992
and Mushak
1998
).
These
findings indicate that children as well as adults can be exposed to serious
risks to their intellectual and cognitive development at lead levels in drinking water
that are easily achievable in many homes in Canada and the US under the current
Maximum Contamination Levels (MCL). Although many steps have been taken
over the years to reduce the amount of lead in water, dangerously high levels of lead
exposure in drinking water can occur in major cities. In 2003, many homes in
Washington DC were found to have lead levels of over 15
g/L. This prompted the
District of Columbia Water and Sewer Authority to take action by replacing lead
service lines, installing water
µ
filters in homes, and adding phosphoric acid to reduce
the corrosivity of the water. According to Maas et al. (
2005
), since the 2003 event,
lead above 10
µ
g/L can still be found in 15 percent of homes in DC when the 6 h
stagnation protocol is used to measure lead. An independent testing conducted in
2009 at six public schools in Washington DC found elevated lead levels in up to
41 percent of drinking sources (Triantafyllidou et al.
2009
). Washington DC was
not the only region to experience elevated lead levels in drinking water in public
schools. An examination of drinking water lead levels in 292 public schools in
Philadelphia indicated over 57 percent (168) of schools had lead levels over 20
g/
L (Bryant
2004
). Even more alarming was that 34 schools had lead levels between
50 and 100
µ
µ
g/L and a further 50 schools had lead levels above 100
µ
g /L.
10.2.3 Social Costs of Lead in Drinking Water
Grosse et al. (
2002
) used data from 1976 onwards to calculate changes in worker
productivity related to BLL. Their
findings can be summarized as follows:
(1) While using the assumption that IQ points decrease by 0.185
0.323 for every
-
1
µ
g of lead per dL, each IQ point raises worker productivity by 1.76
2.38
-
percent;
(2) The value of one IQ point in 2000 dollars lies within the range of $12,700 and
$17,200;
(3) The economic gain from reduction of lead levels for each individual
is
$83,800, while
(4) The overall gain to society can lie between $110 and $318 billion (in constant
2000 dollars).
$29,000
-
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