1.6 How can manganese affect children?

Adverse health effects have also been observed in children who cannot get rid of extra manganese from their body,
such as children whose livers do not function properly. These effects include a lack of control over movements in their
arms and legs, a tendency to overbalance when walking, and uncontrollable shaking in their arms and hands. In addition
to children with problems removing excess manganese from their bodies, some, but not all, children who must have
liquid-form nutrition injected into their veins, called total parenteral nutrition (TPN), have also shown these effects. In the
cases involving liquid diets, the children had no control over the foods they ate, and there may have been too much
manganese in the liquid food. These same effects have been observed in adults with similar liver conditions or on liquid
diets. More serious health effects are typically observed only in people who have inhaled manganese in a work
environment for many years. These occupational environments tend to have manganese levels that are much higher
than the typical environment (10–70 nanograms/m³ in urban areas with no significant sources of manganese). The
severe and permanent neurological effects and mood swings that might be anticipated from occupational studies of
adults have not been reported in children. Workers who have been overexposed to manganese particles in the air have
suffered wild mood swings, uncontrollable laughter or crying at inappropriate times, and abnormal facial expressions
(stiff with grimacing or blank with no expression). Similar effects have also been seen in monkeys who have been
injected with low levels of manganese for only a few days. These serious effects of manganese overexposure might be
expected in children who have been exposed to high concentrations of manganese for extended periods, although it is
not known for sure. The levels of manganese children would have to breathe or eat before they showed these effects is
not known.

Limited information suggests that higher-than-usual amounts of manganese can cause birth defects. One study in
humans suggests that high levels of exposure to environmental manganese (in the soil, water, air, or food) might
increase the chances of birth defects. However, it is not possible to reach a conclusion from this study because other
factors were present that may have caused the birth defects. Studies involving animals exposed to manganese in air are
limited. One study in animals shows that exposure of pregnant females to high levels of manganese in air resulted in
decreased body weight in the pups. Other studies investigating birth defects have used different exposure methods.
One study that involved exposing pregnant rats and their offspring to manganese in drinking water (over 21,000 times
the amount that is typically recom­mended as safe for people to eat each day) found that the rat pups had a short-lived
decrease in body weight and an increase in activity. Higher concentrations (approximately 37,000 times the
recommended safe amount for humans) of manganese provided in food to animals were associated with decreased
activity, while lower concentrations (approximately 1,100 times the recommended safe amount for humans) given all at
once each day to rodents can cause delays in the growth of reproductive organs, decreased pup weight, mistakes in
skeletal formation, behavioral differences in animals, and changes in the brain.

Other studies in which pregnant animals have been injected with manganese show that negative effects can be seen in
unborn pups. These studies have reported delays in formation of skeletal bones and internal organs, suggesting that
the skeletal system is a target for birth defects caused by manganese. However, except when manganese is
administered via a liquid form of nutrition injected into their veins, humans are not exposed to manganese through

Because manganese is a normal part of the human body, it is always present in the tissues and bloodstream of the
mother; in addition, it can cross the placenta and enter an unborn baby. Manganese has been measured in plasma from
the umbilical cord blood of premature and full_term babies, as well as in the blood of their mothers. The concentrations
of manganese found in full_term babies were slightly higher than the concentrations found in premature babies, though
these levels were not significantly different. Also, manganese levels in the livers of pregnant rats were much higher than
those in non-pregnant rats, and the manganese levels in their unborn pups were higher than usual. Although the few
available animal studies indicate that excess manganese interferes with normal development of the fetus, the relevance
of these studies to humans is not known. There is no information available on the effects in pregnant women from
exposure to excess levels of manganese in air, food, or water.

Manganese is necessary for proper nutrition for a rapidly growing infant. The element is present in breast milk at
approximately 4–10 µg/L, an amount that appears to be adequate for a nursing baby. Studies show that infant formulas
contain more manganese than breast milk, but that infants absorb the same proportion of manganese from infant
formulas, cow's milk, and breast milk. However, because cow milk formulas and soy formulas contain much larger
amounts of manganese than breast milk, infants who are fed these formulas ingest much higher amounts of manganese
than breast-fed infants. Whether these higher amounts of manganese are unhealthy for the infant is unknown.