Manganese exposure in foundry furnacemen and scrap recycling workers

Cast iron products are alloyed with small quantities of manganese, and foundry furnacemen are potentially exposed to manganese during tapping and handling of smelts. Manganese is a neurotoxic substance that accumulates in the central nervous system, where it may cause a neurological disorder that bears many similarities to Parkinson's disease. The aim of the study was to investigate the sources and levels of manganese exposure in foundry furnacemen by a combined measuring of blood-manganese (B-Mn) and manganese in ambient air (air-Mn).

During a period of 16 months, Air-Mn and B-Mn (denoted 'exposure values') were measured involving 24 furnacemen employed in three small size foundries and 21 scrap recycling workers from one plant. In the study period, 18 furnacemen had B-Mn measured 3-4 weeks after decreasing or stopping exposure (denoted 'post-exposure values'). The reference group for the B-Mn measurements consisted of 90 Danish male subjects.

Furnacemen who work in insufficiently ventilated smelting departments inhale, absorb, and retain significant amounts of manganese in their blood (approx. 2.5-5 microg/l above reference values) despite a generally low measured airborne level of manganese fumes (0.002-0.064 mg/m(3)). The 'exposure values' compared with 'post-exposure values' revealed a significant decrease in the B-Mn (on average 3.7 microg/l) level of the most exposed furnacemen. Two persons in our study were suspected of suffering clinically subacute manganese intoxication as both had B-Mn levels beyond the normal limit (25 and 29 microg/l, respectively). The potential problem disappeared completely after cessation of exposure, and the B-Mn levels decreased to 9.4 and 14.1 microg/l, respectively.

Risk assessment based on combined measurements of B-Mn and air-Mn seems to be valid in the interpretation of workers' hazard. Our study indicates that B-Mn may be a valuable parameter for estimating recent exposure (within 1-2 weeks). However, more knowledge is needed about the B-Mn level and its relation to neurological symptoms.