A recent article, published in Occupational Medicine, reported on cases of occupational asthma caused by acrylic compounds, which were recorded in the SHIELD surveillance scheme, between 1989 and 2014.[i] In the past, there have been case reports which discuss respiratory sensitisation to acrylic compounds in operating theatre staff, optical laboratory technicians, assembly and manufacturing operatives, beauticians, automotive repairers, printers, a graphic arts worker, a secretary, a plumber, dental personnel and model makers. The aim of this research was to divulge all notifications to SHIELD where occupational asthma had been caused by sensitisation to acrylic compounds, in order to illustrate both common, and new, examples of occupational exposures.
Acrylics, or poly-acrylates, have been used since the 1930s as adhesive resins, surface coatings, synthetic textiles, printing ink and hard plastic. The most commonly produced acrylic is methyl acrylic, which is traditionally involved in the manufacture of poly methyl acrylic (PMMA), which is used to make hard contact lenses and transparent replacements for glass such as Perspex. It is also used as a dental filler and adhesive, orthopaedic bone cement, histological fixation medium and gel for nail extensions. Skin sensitisation to acrylics was recognised as early as the 1940s and has been found in assembly workers, dental staff and nail technicians.
SHIELD is the Midland Thoracic Society’s Surveillance Scheme of Occupational Asthma.[ii] It is a voluntary scheme, by which respiratory and occupational physicians contribute towards the reporting of cases. Cases are noted when positive clinical diagnosis of occupational asthma proves ‘more than likely’, provided there is evidence of occupation-related asthma, demonstrating a worsening of symptoms, and a symptomless latent interval, prior to the onset of symptoms. Pre-existing asthma, only exacerbated by work, was not included.
Out of 1,790 occupational asthma cases reported to SHIELD in the West Midlands, between 1989 and 2014, 20 were due to acrylic compounds, of which 8 were predominantly due to methyl methacrylate. The latency period between first exposure and onset of symptoms ranged from 5 months to 26 years, with a median of 36 months. There were 11 patients with atopy (the genetic tendency to develop allergic diseases such as asthma, eczema and hayfever).
A variety of exposures and industries were implicated, including: manufacturing, health care, beauty, printing and education. Agents containing acrylic compounds were commonly sourced in adhesives, emulsions, coatings and bone cement, printer ink, nail extensions, dental filler and injection moulding substances. A novel presentation was found in teachers exposed to floor adhesives.
A strength of this study was its large size, while its main weakness was that specific inhalation challenge (SIC) testing did not confirm the patients’ respiratory sensitivity, when exposed to the suspected causal agent. SIC testing is used in many European studies, perhaps because it is required if compensation is sought. In the UK, however, objective demonstration of a work-related pattern for asthma (including a latency period and relief from symptoms when away from work), obtained through repeated peak flow testing, plus a history of exposure to a sensitising agent, would usually be sufficient for awarding compensation under the government Industrial Injuries Disablement Benefit (IIDB) scheme.
The role of atopy in occupational asthma due to low-molecular-weight agents (e.g. the molecules that combine to make acrylics) remains controversial. Some studies report that atopy confers an increased risk of occupational asthma, and some found no association. This remains unclear for some agents commonly associated with occupational asthma, such as isocyanates and platinum salts. In the current study, 55% of patients were atopic, which is a little higher than reported in earlier studies.
Although 1% of occupational asthma cases reported to SHIELD during the 25 year period were attributed to acrylic compounds, interestingly, 26% of all SHIELD notifications are for workers employed in occupations associated with reported cases of sensitisation to acrylic compounds (health and dental care, assembly, plastic moulding, beauty, laboratory work). Thus, many workers exposed to acrylic are also exposed to other agents associated with occupational asthma.
The researchers concluded that acrylic compounds remain an important cause of asthma at work, and exposure can occur in a wide variety of industries.
[i] Walters, G. I., Robertson, A. S., Moore, V. C. & Burge, P. S. Occupational asthma caused by acrylic compounds from SHIELD surveillance (1989–2014). Occup Med (Lond) 67, 282–289 (2017). https://academic.oup.com/occmed/article-abstract/67/4/282/3744546/Occupational-asthma-caused-by-acrylic-compounds?redirectedFrom=fulltext (Accessed 8th June 2017)
[ii] Shield - Surveillance Scheme for Occupational Asthma. Available at: http://www.occupationalasthma.com/shield.aspx (Accessed: 8th June 2017)