Workplace exposure to chemicals causing irritant-induced asthma – industry and agriculture as the key risk trades

Inhalation of corrosive or highly oxidising chemicals can lead to the development of asthma - either as a result of repeated exposure or accidental exposure. A recent study by the Finnish Institute of Occupational Health suggests that Finnish workplaces and occupational health services do not always identify substances that are severely irritating to the respiratory tract well enough and do not understand the effects of high concentrations on health.

The Finnish Institute of Occupational Health examined occupational asthma caused by irritation in Finland in 2000–2018.

"About half of the asthma cases developed as a result of a single, accidental exposure, and half were related to repeated exposure events - in some cases, the high exposure and also the symptoms had continued for years," says Irmeli Lindström, Chief Medical Officer of pulmonary diseases at the Finnish Institute of Occupational Health.

The development of asthma can be caused by a situation in which an employee inhales high concentrations of corrosive acids, bases or strong oxidising agents that cause damage in the airways. The single the most common unique causative in the study data was sulphuric acid. Other typical causes of occupational asthma were other corrosive acids, ammonia, lye, chlorine gas, hydrogen sulphide, various combustion gases, and alkaline dusts.

Katri Suuronen, Senior Advisor, and Satu Soini, Specialist in occupational health services, from the Finnish Institute of Occupational Health outline that we should not accept working conditions with exceeded Occupational Exposure Limits.

The research results are also internationally significant, and it is important to take the findings into account in the workplace, occupational health care, occupational safety and health as well as occupational safety supervision. While preventing asthma caused by irritation in the workplace, other long-term respiratory diseases, such as long-term rhinitis and sinusitis, are likely to be reduced.

Shortcomings in knowledge and the flow of information

The research examined the underlying causes that have led to occupational asthma.

In the case of asthma caused by a single exposure event, the main cause was lack of information, disruption of information flow, or incorrect instructions. In contrast, asthma caused by repeated exposures was generally due to poor working conditions in three out of four cases.

"If the substance is highly corrosive and the concentration is high, lungs can be damaged in just a few breaths. Based on both previous studies and our findings, some develop more severe asthma. In this case, despite medication, the symptoms of asthma persist, physical performance can decline, and the illness can lead to significant permanent harm," says Irmeli Lindström.

Exposures have occurred in several industries and many occupations

The study identified stationary plant and machine operators and repairers in the chemical, pulp, metal and mining industries as risk occupations. In addition, several cases were reported among farmers as well as workers in the food industry, construction and transportation.

"It was remarkable that in heavy industry, in several exposure cases, employees had been exposed to high levels of irritants when performing their normal work tasks, and not during exceptional situations," says Irmeli Lindström.

Typical exposure situations were process leaks and repair tasks in heavy industry and various fires and heating of materials. The emptying of sacks or silo breakdowns could expose employees to strongly alkaline dust such as ash and cement dust. In agriculture, sludge handling and emptying of sludge wells caused exposure to ammonia and hydrogen sulphide from animal faeces and urine. In some exposure cases, strong detergents have been used by spraying and employees have worked without protective equipment.

Irritant-induced asthma project

  • The research investigated the causes of occupational asthma, the occupations and exposure events in 69 patients.
  • The results are published in the prestigious occupational medicine journal Occupational and Environmental Medicine.
  • The irritant-induced asthma research (2020–2022) is funded by the Finnish Work Environment Fund, the Research Foundation of the Pulmonary Diseases and, through the Faculty of Medicine of the University of Helsinki, Finance Finland, the Finnish Workers' Compensation Center and the Finnish Motor Insurers' Centre.
  • Next, a team of researchers at the Finnish Institute of Occupational Health will study the prognosis of irritant-induced asthma and its effect on work ability.
  • More information about the project (in Finnish): Ärsytysastma (2020–2022) - Työterveyslaitos (

More information

  • Irmeli Lindström, Chief Medical Officer, the Finnish Institute of Occupational Health, tel. +358 (0)46 8511 1898, irmeli.lindstr%C3%B6m [at] (irmeli.lindström[at]ttl[dot]fi)
  • Satu Soini, Chief Medical Officer, the Finnish Institute of Occupational Health, tel. +358 (0)46 851 5858, satu.soini [at] (satu[dot]soini[at]ttl[dot]fi)
  • Katri Suuronen, Senior Advisor, the Finnish Institute of Occupational Health, tel. +358 (0)40 555 3510, katri.suuronen [at] (katri[dot]suuronen[at]ttl[dot]fi)

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