Geology Reference
In-Depth Information
absence of lead in the household plumbing system. Most house-
holds in the UK conform to the EC standard of 50 mgL
1
and a
concentration of 4 mgL
1
may be taken as representative. Gas-
trointestinal absorption of lead from water and other beverages is
highly dependent upon food intake. After long fasting, absorp-
tions of 60-70% have been recorded, 14-19% with a short period
of fasting before and after the meal, and only 3-6% for drinks
taken with a meal. If 15% is taken as typical, for a daily
consumption of 1.5 L, intake is 7.5 mg and uptake 1.1 mg.
(iv) Cigarette smoking exposes the individual to additional lead.
While both individual exposure to lead and the uptake eciencies of
individuals are very variable, it is evident that exposure arises from a
number of sources and control or human lead intake, if deemed to be
desirable, requires attention to all of those sources. An additional
pathway of exposure, not easily quantified, and not included above is
ingestion of lead-rich surface dust by hand-to-mouth activity in young
children.
The above calculations estimate that for a typical adult in a developed
country, daily uptake of lead from air, diet, and drinking water is,
respectively 1.4 mg, 6 mg, and 1.1 mg. Exposure to lead from all of these
sources has fallen rapidly over the past 20-30 years. Figure 12 contrasts
the temporal trends in use of lead in petrol (gasoline) and blood leads in
the general population of the UK over the period when much of this
decline took place. It is interesting to note that from 1971 to 1985 use of
lead in petrol was relatively steady, but blood leads declined by a factor
of more than two over this period mainly as a response to reductions in
dietary exposure, particularly associated with the cessation of use of
12
25
Blood Lead
Gasoline Lead
10
20
8
15
6
10
4
5
2
0
1970
0
1974
1978
1982
1986
1990
1994
Year
Figure 12 Trends in lead use in petrol (gasoline) and of lead in the blood of the general
population in the United Kingdom, 1970-1995
