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Biomonitoring studies on exposure of power plant workers to harmful chemicals of ash during ash removal and maintenance tasks indicated low systemic bioavailability. Modestly increased Pb concentrations were observed in blood samples of exposed workers. The average blood Pb concentration of workers (22.8 µg/l) was only slightly higher than the reference value for non-exposed persons (including pregnant women) (18.6 µg/l), and therefore not likely to be associated with adverse health effects. Blood cadmium concentrations (0.787 µg/l) were clearly below the reference value for non-exposed persons (2.023 µg/l). Similarly, concentrations of aluminum, manganese, mercury, arsenic and selenium in urine of the exposed workers were all below the reference values for non-exposed persons. It was recommended that workers, especially those who work inside the power plant boilers or superheaters, should routinely use powered air respirators with TM3-A2B2E2K2-P cartridges, and hooded one-piece coveralls and over-wrist long leather protective gloves.
A retrospective cohort study published in 1988 was carried out on 268 men with a history of more than 10 years exposure to PFA in six power stations in the south east of England. Lung function tests showed that a modest effect on forced vital capacity, vital capacity, forced expiratory volume in one second, peak flow, and gas transfer (DCO) was associated with prolonged heavy exposure to PFA. The men with prolonged heavy exposure also showed higher prevalences of respiratory symptoms. No definite relation between exposure and x-ray changes was established. The results indicate that exposures to PFA should not exceed the limits recommended by the Health and Safety Executive for low toxicity dusts [long-term exposure limit 8-h TWA for pulverised fuel ash: 10 mg/m3 (inhalable dust), 4 mg/m3 (respirable dust)].

Additional information

The occupational exposure studies showed that especially workers involved in ash removal and maintenance tasks inside boilers of power plants are potentially exposed to high concentrations of inhalable dust. However, biomonitoring revealed on average relatively low concentrations of metals in whole blood and urine samples of exposed workers. Workers from recycled fuel-fired power plants had the highest proportion of samples exceeding the reference values of non-exposed population as well as workers with using insufficient or no personal protective gear. The outcome of biomonitoring studies is in accordance with the leaching, dissolution and toxicokinetic studies with Ash that largely indicated low systemic bioavailability of metals from Ash.

The retrospective cohort study on the respiratory effects of prolonged exposure to pulverized fuel ash showed that heavy exposure for 10-20 years or more had only a slight effect on lung function. Only the heavy exposure was also related to a higher prevalence of respiratory symptoms. It can be speculated that the use of personal protective equipment during the work history of the subjects was not according to the current standards.