Anne-Helen Harding and coworkers presented mortality data from 98 117 workers followed-up for 1 779 580 person-years.1 They found an increased mortality due to ischaemic heart disease (IHD), standardised mortality ratio (SMR) 1.40 (95% CI 1.36 to 1.44). The total number of IHDs was 4183 and total number of deaths was 15 496. Many factors (eg, length of exposure, latency, smoking status, main job category) were taken into account when studying several cancers, asbestosis and cerebrovascular disease. However, IHD was not further analysed. There are some good arguments for further scrutinising this cause of death.

Today it is a rather established fact that exposure to particulate air pollutants is associated with increases in mortality and hospital admissions due to respiratory and cardiovascular disease.2 Short-term effects of air pollutants have been studied among 38 million persons in eight European cities. An increase of 10 μg/m³ in particulate matter ⩽10 μm (PM10) was associated with 0.5% (95% CI 0.2 to 0.8%) increase in hospital admissions for cardiac causes.3 A US cohort of approximately 500 000 persons was formed in 1982 and followed for 16 years. Each 10 μg/m³ elevation of fine particulate matter ⩽2.5 μm (PM2.5) was associated with a 6% increase of …