Abstract

Pulverised fuel ash is the residue that remains when pulverised coal is burnt in power stations. Low grade coal, ground to a particle size of 0- 1-100 tm, is blown into boilers in jets of airborne coal particles, and the residual ash is collected in electrostatic precipitators. Pulverised fuel ash is an important byproduct ofthe power industry: it is used for land filling and, because it sets hard in the presence of lime and water, is widely used as a building material in breeze blocks. It has not previously been reported as causing asthma. We report a case of asthma in a worker at a power station that was caused by inhalation of pulverised fuel ash.

Case report
Nine months after staring work as a plant attendant at a power station a 27 yearold man developed episodes of shortness of breath with wheezing, which
improved at weekends and during holidays. His work included cleaning the filters of the bags. On two occasions he was admitted to hospital with acute severe asthma. He had suffered from hay fever since childhood,and skin prick tests with etrmacts of grass pollen and housedust elicited immediate reactions. He recorded his peak expiratory flow rate every two hours for 28 days. This deteriorated during work and improved when he was away from work. He underwent single blind occupational type inhalation tests.Tipping of 250 g of lactose and 2-5 g of charcoal (producing dust that looked like pulverised fuel ash) for 30 minutes elicted no change in his forced expiratory volume in one second, but tipping of 250 g of lactose with 2g of pulveriused fuel ash provroked a late asthmatic ration. this late reation was reproduced by a second inhalation test with the ash. The concentration of histamine required to cause a 20% fall in FEV1 decreased from 12 mg/ml one day before the inhalation test with pulverised fuel ash to 2-5 mg/ml 24 hours after the test. Serum neutrophil chemotacic activity increased by 120% during the late asthmatic reaction.
After these results he was relocated at work to prevent him being exposed to
pulverised fuel ash any longer. He remained free of symptoms and required no
treatment. Serial measurements of PEF after he Was relocated showed no evidence of asthma.
This patient's symptoms suggested that he had developed asthma related
to his work, and this was confirmed by the results of serial measurements of
his peak expiratory flow rate. Inhalation testing with pulverised fuel ash, to which he was exposed at work, provoked a reproducible asthmatic reaction.
This late response was associated with a rise in serum neutrophil chemotactic activity (measured during the second inhalation test). The interval of nine months before the onset of his symptoms, the late asthmatic reaction provoked by the inihalation test with pulverised fuel ash, the associated increase in airway reactivity, and the resolution of asthma after relocation at work suggest that pulverised fuel ash was the primary cause of this man's asthma.
Pulverised fuel ash is a complex material: 60-80%h of its weight is made up
of water insoluble aluminosilicates, 15-30% of crystals (the main species
being mullite, magnetite, carbon, and quartz), and the remainin 24% of
water soluble sulphaes of calcium, sodium, and potassium with trace
quantities of arsenic, boron, copper, molybdenum, and selenium. We did
not identify which ofthese materials, either alone or in combination, caused
our patient's asthma. Some 12 milion tons of pulverised fuel ash are produced each year in the United Kingdom and 50 million tonnes each year in the United States. The greatest risk of developing asthma due to inhaled pulverised fuel ash is run by those working in the power and construction industries.

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