STAMI has carried out several surveys among welders and workers at manganese smelting plants. This is done by measuring
Mn in biological samples in order to study the coherence between concentration of Mn in the air and in the biological samples.
The coherence is best seen when comparing air concentration of Mn and the Mn-levels in urine – especially when the soluble
part of Mn has been taken into account.

The coherence has not been so clear when comparing Mn-levels in air concentration and Mn in full blood and serum.
Little is known of how diurnal variation affects excretion of Mn, but this is a key factor for specifying both when to sample urine and
also to better distinguish exposed and non-exposed individuals.

The monitoring is done by measuring Mn-levels in the urine in the morning, in the afternoon, and before bedtime for
40 exposed tappers and 20 non-exposed workers at three Norwegian manganese plants.
In addition, the workers are carrying air sampling devices in order to measure the content of Mn in the air both test-days.
Before starting a blood sample is also taken for among other things, to measure the iron level.

The results of this study will add new knowledge which can be beneficial for biological monitoring of the occupational exposure to Mn.
This could prove useful for the industry and its employees in that it will facilitate methods for simplifying monitoring of the working environment.