Manganese - Toxicology of Metals - page 635

Manganese intake from drinking water is normally
substantially lower than intake from the median drink-
ing water level of 10

In connection with the levels of manganese in
different foodstuffs, it is interesting to quote a study
on bioaccumulation of manganese by plants. Lytle et al .
(1994) reported increased concentrations of manganese
in fruits and stems of oats grown in the organic and
sandy soils at the station with the highest traffi c den-
sity. In a study (Normandin et al ., 1999) manganese was
measured in the plants (fl ower, stem, leaves, and root).
The authors tried to evaluate the potential of dandelion
( Taraxacum offi cinale ) as a bioindicator of manganese
arising from the use of MMT in gasoline. Mn concen-
trations of the different parts of the plant were not cor-
related with the distance from the roadways.
Residues of maneb (< 0.1-4.0 mg/kg) were detected
in various crop samples obtained from an area where
maneb was used as a fungicide (Pease and Holt,
1977).
In a Canadian study (Méranger and Smith, 1972), it
was estimated that of the total manganese intake, 54%
comes from cereals. The second largest source was
potatoes, which gave 14%, whereas meat, fi sh, and
poultry provided only 2%. However, there is a differ-
ence in manganese concentrations for the same items in
different countries and areas. Daily manganese intake
between 5.8 and 12.4 mg has been reported from vari-
ous regions in India (Soman et al ., 1969), whereas in
the United States (Schroeder et al ., 1966) and Germany
(Schelenz, 1977), average intake by adults has been
estimated to range from 2.1-4.1 mg/day.
Variations in manganese intake can, to a large
extent, be explained by differences in nutritional hab-
its. In populations with cereals and rice as main food
sources, the intake will be higher than in areas where
meat and dairy products make up a larger part of the
diet. Manganese intake can be higher in populations
with a high tea consumption. A cup of tea may contain
0.4-1.3 mg manganese (ATSDR, 2000).
Summing up all the available data, it can be esti-
mated that daily intake of manganese from food
ranges from 2000-8800

g/L. Daily water consumption
is set at 2 L/day. The overall database supports the
value of 0.4 mg/L as a health-based guideline value
(WHO, 2004). Drinking mineral water regularly can
add signifi cantly to manganese intake (Dieter et al .,
1992).
The highest level for manganese in fresh waters to
prevent undesirable taste and discoloration is 50

µ

g/
L (EPA, 1978; WHO, 1981). To avoid staining clothes
or plumbing fi xtures, the EPA recommends that the
concentration of manganese in drinking water not be
more than 0.05 mg/L. The FDA (1993) has set the same
level for bottled water.

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4.1.3 Soil

As a component of earth's crust, manganese occurs
naturally in virtually all soils. Average natural (background)
levels of manganese in soils range from approximately
40-900 mg/kg, with an estimated mean background con-
centration of 330 mg/kg (Cooper, 1984; Eckel and Langley,
1988; Rope et al ., 1988). Accumulation of manganese in soil
usually occurs in the subsoil and not in the soil surface;
60-70% of manganese is found in the sand fraction of the
soil (WHO, 1981). Soil manganese concentrations arising
from the use of methylcyclopentadienyl manganese tri-
carbonyl in unleaded gasoline are apparently connected
with manganese oxides from Mn-containing motor vehi-
cle exhaust (Lytle et al ., 1995). Because they are correlated
with distance from the roadway, it can be concluded that
the environmental fate of manganese from MMT sources
could be associated with increased total manganese in soil
(Normandin et al ., 1999).
The oxidation state of manganese in soils and
sediments may be altered by microbial activity.

4.2 Food
Manganese is a natural component of most foods.
Its concentration in foodstuffs varies markedly, but on
the whole, food constitutes a major source of manga-
nese intake for humans.
The highest manganese concentrations are found in
some foods of plant origin, especially wheat and rice;
here concentrations between 10 and 100 mg/kg have
been reported (Guthrie, 1975; Schroeder et al ., 1966).
Polished rice and wheat fl our contain less manganese
because most of it is in the bran. High concentrations
(up to 50 mg/kg) are found in nuts, tea, legumes, pine-
apples, and whole grains, and lower levels (up to 5 mg/
kg) in milk products, meats, fi sh, and eggs (Davis et al .,
1992; Pennington et al ., 1986).

g (EPA, 1984a; WHO, 1981).
Even though gastrointestinal absorption of manganese
is low (3-5%), oral exposure is the primary source of
absorbed manganese for general population. Adequate
and safe intake of manganese for adults is considered
to be 2-5 mg/day (NAS, 1980). According to some data
from the United States, it is possible that a signifi cant
proportion of Americans, especially females, are not
consuming suffi cient manganese (Davis and Gregor,
1992; NAS, 1980; Pennington et al ., 1986). However,
infants may be ingesting more than the estimated safe
and adequate dose of 0.3-1.0 mg/day for their age
group (Pennington et al ., 1986) because of relatively
high manganese levels in prepared infant foods and
formulas (Lönnerdal, 1997).

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