Asthma on the job

Abstract

Writing in 1700, Bernardino Ramazzini, often cited as the father of occupational medicine, described asthma associated with particular professions, including baking and grain handling. Many centuries earlier, Hippocrates too had noted the presence of asthma-like symptoms among particular groups of workers, including farm hands and metal workers. Understanding the potential effect of workplace exposures on health, Ramazzini proposed that an additional query should be added to the questions that Hippocrates recommended doctors should ask their patients: “What is your occupation?” This question remains pertinent today, according to data published by the US Centers for Disease Control and Prevention (CDC) in April. They estimate that 15·7% of asthma cases among ever-employed people with current asthma from 22 US states were related to work—suggesting a total of 1·9 million work-related cases across the states included in the study. The data were obtained from a large telephone survey done in 2012, in which participants who answered “yes” to having been diagnosed with asthma were asked whether they had been told by a doctor or health-care professional that their asthma was caused or exacerbated by any job they had ever had. This proportion is larger than a previous estimate of 9·0% from a survey of 2006–09, but the authors note that the results are not comparable because of changes to the survey and weighting methods, suggesting that the latest findings should be treated as a new baseline for comparison with later results. The investigators noted substantial variation between states, with proportions ranging from 9·0% in Hawaii to 23·1% in Missouri, and between age groups, with the highest proportion among people aged 45–64 years (20·7%). Work-related asthma is a general term that covers both occupational asthma, wherein new-onset disease is caused by a sensitising agent or airway irritant present in the workplace, and work-exacerbated asthma, in which factors at work can trigger or worsen the symptoms of existing disease. An important limitation of the new CDC data is that it does not differentiate between these different forms of work-related asthma. More information about whether disease was caused by workplace exposures or exacerbated them, and the extent to which patients' lives are affected would be useful for the design and targeting of preventive strategies. Occupational asthma can be further divided by causative agent: sensitising agents can include high-molecular-weight sensitisers such as plant and animal proteins that induce production of specific immunoglobulin E, and low-molecular-weight chemical sensitisers, for which the pathological mechanisms are often less well understood. Additionally, irritant-induced occupational asthma is caused by direct exposure to airway irritants without sensitisation. Hundreds of workplace substances have been reported as possible causes of asthma and more are identified each year. Isocyanates used in spray paints and in the manufacture of foam moulding and other industrial processes are the most common cause of occupational asthma in the UK. According to data presented at the European Respiratory Society's International Congress last year, flour is the most common cause in France, accounting for 20% of cases, recalling the baker's asthma described by Ramazzini. Emergency workers exposed to dust from the collapse of the World Trade Center in 2001 developed what is regarded as an example of irritant-induced occupational asthma. Another limitation of the CDC report is that Ramazzini's question was not addressed—the occupations of participants with possible work-related asthma were not recorded. This is a missed opportunity, but questions about participants' jobs will be added to subsequent surveys. This addition should allow each occupation to be linked with risk of work-related asthma, which could inform public health strategies, workplace interventions, and regulation to reduce disease burden. Despite its limitations, the latest CDC data confirm that work-related asthma is common among working-age adults. Work-related asthma is potentially preventable, and an early diagnosis can result in a full recovery by preventing continued exposure to the sensitising agent. Conversely, if the link between a patient's symptoms and workplace exposure goes unrecognised, the prognosis will get worse. These findings therefore emphasise the need for workers in affected industries to be educated about the risks of work-related asthma, and for health-care workers who see adult patients with asthma to remember to ask Ramazzini's question, to ensure that the opportunity to help such patients is not missed.