Occupational Risks and Acute Myocardial Infarction

Background

Acute myocardial infarction (AMI) is the medical term for a heart attack and occurs when blood flow to the heart decreases or stops, usually caused by blockages in the arteries [1]. In 2015, there were 240,060 cases of AMI in adults aged 20 years or older in Ontario [2,3]. Adults with a history of AMI are four times more likely to die of any cause compared to those without, demonstrating the importance of continued efforts to understand and prevent AMI [4]. AMI risk is most often attributed to behavioural factors including smoking, poor diet, alcohol consumption, and physical inactivity [5]. However, there is growing evidence for occupational risk factors related to increased risk of AMI.

Possible occupational risk factors for AMI include noise, vibrations, temperature extremes, secondhand smoke, chemical and particulate hazards, shift work, psychosocial stress, and occupational physical activity [6-14]. Exposure to noise increases blood pressure, an established risk factor for AMI, though an association with AMI is less well established [7,12]. Exposure to vibration has been shown to influence changes in heart-rate variability and peripheral vascular contraction, both risk factors for AMI [15]. Temperature extremes like heat and cold and specific toxins like carbon monoxide from diesel engine exhaust and environmental tobacco smoke may also increase the risk of heart disease [9]. Exposure to particulate air pollution, including silica dust, fumes, and combustion particles have been shown to be associated to increased risk of AMI [8].

Other factors like shift work may also increase risk of heart disease, however, findings have been inconsistent [11]. There is also some evidence that psychosocial exposures can lead to job strain causing psychological stress, possibly affecting heart health. Job-related stress is related to socioeconomic status, which is a strong predictor of AMI [14,16]. There is increasing evidence suggesting that blue-collar workers are at increased risk for AMI compared to white-collar workers [6,14,17]. Although blue collar workers may experience more occupational physical activity, which is often recognized as a preventable factor for heart disease, these workers are likely to experience heavy lifting and manual labour which may increase the risk for heart disease [9].

Occupational Disease Risks

The following results show the percent increase in risk among groups of workers by industry or occupation compared to all other workers followed in the ODSS. In the ODSS worker cohort, AMI risk was generally higher among blue-collar workers compared to white-collar workers, similar to previous studies [14].

 

Wood-related work

A consistent excess risk of AMI was observed for workers in wood-related industries and occupations in the ODSS. Use of tools and machinery, such as industrial woodworking equipment and chainsaws in forestry and logging, may lead to exposure to excessive noise and vibration [12,15]. Other occupational exposures that may increase AMI risk for wood-related workers include psychosocial stress (from job strain or stressful work conditions) [18] and shiftwork [19-20] and among pulp and paper mill workers, exposure to sulfur compounds and bleachery chemicals [20-22].

Industry or Occupation Increased risk
Wood manufacturing industries 27%*
    Wooden box factories 57%*
    Veneer and plywood mills 40%*
    Sawmills, planning mills, and shingle mills 32%*
    Sash, door and other millwork plants 26%*
Forestry and logging occupations 33%*
     Log hoisting, sorting, moving and related 74%*
     Timber cutting and related 27%*
Wood processing (except paper pulp) occupations 50%*
     Labouring and other elemental work 71%*
Pulp and papermaking occupations 31%*
*Statistically significant (α=0.05)


Mining and quarrying

Increased risks of AMI were observed for specific mining industries in the ODSS. Exposure to noise and vibration through drilling, blasting, crushing or other operations in mining and quarrying workers can increase the risk of AMI [15]. Miners are also exposed to diesel engine exhaust and particulates such as respirable quartz, which have been associated with increased risks of AMI [8, 23-26].

Industry Increased risk
Sand pits or quarrying 61%*
Gold quartz mining 52%*
Uranium mining 37%*
*Statistically significant (α=0.05)

 

Textile manufacturing and processing

Increased risks of AMI were observed in textile manufacturing workers which has been previously observed [27]. Workers may be exposed to a variety of organic dusts and airborne particulate from fibrous material that is often contaminated with bacterial endotoxins [28]. Inhalation of dust and endotoxins may contribute to increased risk of AMI [8, 29]. The highest risk of AMI in this group was for textile fibre preparing, finishing and calendaring.

Industry or Occupation Increased risk
Leather industries 48%*
Textile processing occupations 26%*
     Textile fibre preparing 165%*
     Textile finishing and calendaring 124%*
*Statistically significant (α=0.05)

 

Excavating and grading

Construction work is physically demanding and workers in this sector are regularly exposed to loud noise, vibrations, and stressors [24, 30]. An excess risk of AMI was observed in excavating, grading and related work labourers. Workers may also be exposed to diesel engine exhaust, crystalline silica dust, and polycyclic aromatic hydrocarbons which have been linked to increased cardiovascular disease risks [24, 31-33].

Occupation Increased risk
Labouring and other elemental work: Excavating, grading and related 38%*
*Statistically significant (α=0.05)

 

Truck transport

Increased risk of AMI was observed among truck transport workers, with the highest risk observed among female drivers [14]. An excess among female truck drivers has not been reported before but previous studies have often been limited due to small numbers of female workers [34]. Some studies have shown a higher risk for heart disease in females exposed to airborne particulate matter, compared to males [8]. Truck transport workers are also exposed to high levels of noise and carbon monoxide through diesel engine exhaust, both which have been associated to adverse cardiac effects [12,24,33,35]. Psychosocial stressors including shift work and long working hours may also play a role in AMI risk as long-haul drivers and long-distance drivers have shown an increased risk for AMI in previous studies [19,27,36].

Occupation Increased risk
Female truck drivers 68%*
Male truck drivers 32%*
*Statistically significant (α=0.05)

 

Risk Recognition

Focusing on heart health earlier in life can help to manage risk factors and prevent early heart disease. Behavioural factors such as a healthy diet and weight, engaging in physical activity, stress management, and not smoking are all important for reducing risk of heart disease [37]. However, it is important to understand that occupational factors may also contribute to risk of heart disease [38].

With increasing evidence of occupational risks for AMI, efforts should be made to improve understanding of occupational exposures and specific groups identified in the ODSS. This can lead to better risk reduction strategies for heart disease while also improving workplace health and safety.

References
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Surveillance Bulletins

The Occupational Disease Surveillance System (ODSS) Surveillance Bulletins provide summaries of occupational exposures and disease risks across different industries and occupational groups. The aim of these bulletins is to report on high risk occupations and industries and specific exposures detected through occupational disease surveillance. At this time the ODSS includes workers from 1983-2014 and follows their health outcomes until 2016. This bulletin reflects only the diseases currently tracked within the ODSS. The system is updated and expanded on an ongoing basis.

More information about the ODSS including data sources, methods and detailed results can be found at ODSP-OCRC.ca and OccDiseaseStats.ca.