Chemistry Reference
In-Depth Information
(reviewed in Chang and Page, 1996). Unless com-
plexed to organic matter, nickel in soil primarily
exists as divalent cations. Near nickel refi neries or in
dried sludge, levels of nickel have been found to be
24,000-53,000 ppm Ni in soil, up from the nonindus-
trial average level of 500 ppm Ni (US EPA, 1990). For
example, in the soil and lake sediments of the nickel
mining region of northwestern Russia, it was esti-
mated that during 60 years of mining/refi ning activity,
310 tons of Ni, plus another approximately 200 tons
of other metals and mercury, have accumulated in the
lake sediments, which are a secondary source of pollu-
tion (Dauvalter, 2003). During this century, the average
concentrations of nickel in superfi cial sediments have
increased by approximately 25 times. Metal, including
nickel, contamination of garden soils may be wide-
spread in urban areas because of past industrial activ-
ity and the use of fossil fuels; however, risk assessment
models do not predict health risks from reuse of such
soils for growing food crops in urban redevelopment
areas (reviewed in Hough
et al
., 2004).
Nickel levels in natural waters have been found to
range from 2-10
these levels are stable over time as measured from 1993
to 1997 (Larsen
et al
., 2002). Estimates of total dietary
intake of nickel average approximately 200-300
g/
day, although oral nickel intake because of leaching
from cooking ware, kitchen utensils, and water piping
can perhaps be as high as 1 mg/day (Grandjean, 1984).
It has been suggested that only 5% of ingested nickel is
absorbed (Rojas,
et al
. 1999). Infants can ingest 5-15
µ
g
Ni/day from breast milk. The mean concentration of
nickel in breast milk was measured at 17
µ
g Ni/kg,
exceeding the mother's serum nickel levels (Feeley
et al
., 1983).
µ
4.1.3 Skin Absorption
Nickel absorption through skin contact is a major
human exposure route, with a large portion of the pop-
ulation suffering from contact dermatitis and nickel
allergy. Whereas nickel contact dermatitis was previ-
ously reported to occur in up to 10% of women but only
1% in males (WHO, 1991), recent estimates have nickel
sensitivity approaching 30% of populations, again more
prevalent in females (Brydl
et al
., 2004). An increasingly
large variety of sources of nonoccupational nickel expo-
sures include common objects such as nickel-plated tools
and utensils, jewelry, coins, orthodontic braces and wires,
and surgical joint prostheses. On the basis of increasing
incidences of allergic contact dermatitis because of nickel
and other metal exposures from household items, it has
been recommended that such items contain no more
than 1-5 ppm each of Ni, Cr, or Co (Basketter
et al
., 2003).
In the European Union (EU) the “Nickel Directive” lim-
its nickel content and release from jewelry (e.g., < 0.05%
in pierced-earring posts) and other routinely used metal
items and utensils to minimize chronic nickel exposure
(<0.2
µ
g/L in fresh and tapwater and from
0.2-0.7
g/L in marine water (reviewed in Rojas,
et al
.,
1999). A survey of U. S. surface water indicated that
the concentrations range from 5
µ
g Ni/L in
different regions of the country (US EPA, 1990). The
maximum contaminant level (MCL) of nickel allow-
able in drinking water for lifetime consumption, as
established by the US EPA (1993), is set at 0.1 mg Ni/L.
Average total nickel concentrations in drinking water
range from 3-7
µ
g-600
µ
µ
g Ni/L, with concentrations up to
35
g Ni/L occasionally encountered (Andersen
et al
.,
1983). In areas of nickel mining, however, up to 200
µ
g
Ni/L drinking water have been recorded (McNeely
et al
., 1972). The US FDA limits nickel in bottled water
to 0.1 mg Ni/L.
µ
g/cm
2
/week) and resulting sensitization and der-
matitis (Liden and Norberg, 2005). Even the new 1- and
2-Euro coins that are composed of nickel alloys release
nickel at levels that exceed the limits allowed by the
European Union Nickel Directive. In a study of skin sen-
sitivity to the Euro coins, eczematous skin reactions were
observed, particularly in individuals with nickel sensi-
tization (Seidenari
et al
., 2005). However, it was noted
that daily contact with these coins would most likely be
temporary, mitigating the hazardous effects except for
occupational exposures or for individuals with nickel
sensitivity.
µ
4.1.2 Food Intake
Ni ingestion in humans occurs through the con-
sumption of plant and animal products. Vegetables
such as legumes, spinach, lettuce, and nuts contain
more nickel than other food items. In plants such as
potatoes and corn, metals including nickel are prima-
rily ligated to polysaccharides such as amylose and
amylopectins (Ciesielski and Piotr, 2004). Other die-
tary sources of nickel exposure include baking pow-
der, cocoa powder, and acid beverages, perhaps
related to leaching during manufacturing from pipes
and containers. In Western countries, nickel levels are
generally <0.5 mg/kg fresh weight for produce, except
for cacao and nuts with much higher levels in the 5-
10 mg/kg range (reviewed in Rojas
et al
., 1999), and
4.1.4 Tobacco
Exposure to nickel can occur from cigarette smok-
ing. The International Agency for Research on Cancer
(IARC) lists 9 of the 44 “Group 1 human carcinogens”
in mainstream cigarette smoke (Smith
et al
., 1997). These
