Lung retention and clearance of welding fumes were followed during the years 1976–1982 among 48 shipyard arc welders. The subjects were divided into four groups according to their average exposure time, which varied from 3 to 49 yr. The amount of lung-retained dust was estimated using magnetopneumography. The results indicate that the average clearance rate was 20% per yr. The individual clearances varied between 10 and 30% per yr. Improvements in hygiene in the shipyard were clearly seen in the changes of lung retention rates.

Nearly all metal dusts contain iron, which is one of the most common constituents in steel. Iron has one common ferrimagnetic oxide, magnetite. Although it is considered nontoxic, magnetite can be used as a tracer for more active and pathogenic constituents of inhaled dusts. After the chest area has been magnetized, magnetite produces a weak remanent magnetic field around the body. The field is measured and the amount of dust in the lungs is calculated on the assumption that the composition of lung dust is the same as that of airborne dust. This method has been applied to shipyard and stainless steel welders, to iron and steel workers, to stainless grinders, and to foundry workers. A clear magnetic signal was found for each subject. The maximum amount of lung dust found thus far was 10 g in the lungs of a stainless steel electrode welder. Referents showed signals of 0.5 mg magnetite or less.

An instrument for measuring the specific remanent moment and the pulse coercive force of ferro/ferrimagnetic dust samples has been constructed using a commercial fluxgate magnetometer as a detector. The minimum amount of dust needed for successful measurements is about 1 mg to match the amount of dust collected when using standard air sampling methods. An output noise of 14 PTrms(smooth RC = 48 s)...

Ferrimagnetic metal aerosols originating from the processing of various steels and the resulting occupational exposure have been studied. A description of the phases of steel production is given and the respective dust emissions are characterized using chemical, physical and electronoptical analysis methods. Special attention has been paid to iron, chromium and nickel compounds. Recent developments of the magnetic measuring method for lung-retained ferrimagnetic dust are described, and the results compared with cumulative dust concentrations. The significance of urinary chromium and nickel concentrations as indicators of exposure has been evaluated. The results show that the solubility properties and the chemical composition of chromium and nickel compounds vary greatly between the different handling stages of stainless steel. Alveolar retention of fumes from manual metal arc welding of stainless steel seems to exceed that of the other dusts under study.

The magnetic method of measuring the amount of lung retained contaminants as well as urinary chromium and nickel determinations have been performed among 83 stainless steel (SS) welders who have used matural metal arc (MMA) and tungsten inert gas (TIG) welding techniques. The welders were divided into four groups according to the time percentage used for MMA welding. Only exposure to MMA/SS welding fumes resulted in clearly elevated chromium concentrations in the urine, the correlation coefficient between the values of urinary chromium and MMA/SS percentage being very significant (P < 0.001). Among the smokers the urinary chromium values were increased (P < 0.05) perhaps owing to contaminated cigarettes. In many workplaces the urinary chromium values of several welders exceeded the value of 30 μg/l which is the recommended reference value in Finland. Owing to the solubility properties of nickel compounds in SS welding fumes urinary nickel concentrations were only slightly elevated among MMA/SS welders, and therefore, the urinary nickel determinations do not reflect the level of exposure to nickel compounds. The measured average remanent magnetic field of the chest area correlated well (P < 0.01) with the use of the MMA technique. A very significant correlation (P < 0.001) existed between the average remanent magnetic fields of the chest and the urinary chromium values of MMA/SS welders.

In Finland the amount of lung-retained contaminants has been measured among welders, foundry workers, and iron and steel factory workers. About 300 subjects have so far been measured since 1976. The method of measuring is based on the magnetic properties of metal aerosols. At the very beginning the method resembled the one suggested by D. Cohen. The original method was too slow, and data processing was not suitable for clinical or hygienic work. Therefore, the automatic and computerized instrument for measuring lung-retained contaminants was developed in cooperation with Outokumpu Oy. The resolution of the magnetic measurement is better than 0.05 nT corresponding to a sensitivity of 0.5 mg of magnetic contaminants in the lung in the form of magnetite. These figures mean that, in practice, a shipyard welder has enough contamination for measurement after one month's exposure. In addition, the present paper reviews the magnetic properties of metal aerosols briefly and summarizes the results of measuring different occupational groups.

A long auditory stimulus elicits a magnetic evoked response in the human brain, consisting of transient deflections followed by a sustained response. The distributions of the magnetic fields indicate that the auditory evoked transient response at a latency of 100 ms as well as the auditory sustained response are generated at and around the primary auditory cortex.