"We're aiming for a world where people no longer get sick as a result of their work."
Diesel, pesticides, paint, or composite. Researchers Susan Peters and Sirwan Darweesh envision a future where people no longer get sick from occupational exposure to hazardous substances. We now have a lot of knowledge about the chemicals that cause specific diseases – e.g. pesticides that trigger Parkinson's – but the list is far from complete. The researchers are working hard to address that situation. "Everyone deserves a safe workplace, and we want to make sure people don't get sick because of their work."
"Occupational diseases caused by hazardous substances are preventable," explains Susan Peters. Peters is an occupational epidemiologist at the Faculty of Veterinary Medicine (Institute for Risk Assessment Sciences) and a member of the Occupational Disease List Advisory Committee (see box). "We know a lot about hazardous substances, but we need to figure out which kinds of occupational exposures lead to which diseases. We can then start focusing on prevention so that people don't get sick as a result of their work."
The onset of Parkinson's disease
Sirwan Darweesh couldn't agree more. The neurologist-in-training at Nijmegen's Radboudumc is studying Parkinson's. "I'm mainly focused on the onset of the disease, the period before people actually develop Parkinson's. There are clear indications that this period could last as long as 10 years, or even longer. Environmental factors play a major role in that process."
Which professions expose people to occupational diseases?
"When it comes to pesticides, that's mainly the agricultural sector," Peters explains. "In the construction industry, workers may often be exposed to silica, which are the hazardous particles released when you saw, cut or grind bricks, for example. People working in the construction and transport sectors are exposed to diesel emissions. However, there are also plenty of examples of occupational diseases in the food industry, like bakers contracting allergic asthma from substances in flour. It affects people in all kinds of industries."
Has the number of occupational diseases increased?
"From the 1960s and 1970s onwards, workplace exposure to most substances has clearly been declining," Peters replies. "But that downward trend isn't enough, and people are still being exposed to substances that can make you sick, we know. There's definitely room for improvement."
"Parkinson's is actually significantly more common than it was 50 years ago," Darweesh adds. "We've seen a rapid increase in the number of cases worldwide, but we don't know whether it's because people are getting Parkinson's at an earlier age, or whether it's a result of an ageing population. Parkinson's mainly affects middle-aged and elderly people."
Could that be due to worsening air pollution?
"It's possible yes," Darweesh replies. "But it could also be because people are exposed for longer periods of time because they are living longer. Someone who gets Parkinson's today might not have lived to be 75 thirty years ago."
Isn't it a bit of a pipe dream to think we can stop people getting sick from occupational exposure?
Peters nods in agreement. "That's a valid question. We now know quite a bit about carcinogens these days, but we still expose people to them. Diesel increases the risk of lung cancer, but there are still lots of diesel engines and trucks. The same goes for pesticides. There are a lot of interests at stake. Completely eliminating pathogens might be a pipe dream, but we need to minimise exposure levels as much as we can."
What will that involve?
Darweesh: "As a first step, we need to accurately identify the external factors that contribute to the development of diseases like Parkinson's. Next, we'll need to significantly reduce exposure to those substances in conjunction with policymakers. That's not as easy as you might think. For example, farmers have a relatively greater incidence of Parkinson's than people in other occupational groups, which may be related to high pesticide exposure. I think they're victims of the current situation because they don't have any good alternative income sources."
But surely manufacturers don't want to sell products that make people sick?
"Does that also apply to the tobacco industry?", Peters asks. "Money is an important factor. The harmful effects of tobacco had been known for a long time, but the tobacco industry lobbied a lot to delay regulation. That happens a lot, and it's very frustrating. Still, changes also have to be feasible; you can't suddenly replace all the diesel engines in the world, for example. I agree with Sirwan that it ultimately comes down to prevention policies."
What's the biggest challenge you're facing?
Peters: "Diesel is the biggest issue, as far as I'm concerned. We know it causes lung cancer, but there's still so much to be done worldwide if we want to replace diesel engines. Silica increases the risk of lung cancer, but construction workers are still exposed to it. Another example would be composite kitchen worktops: silica gets released every time you cut them to size. Those particles end up deep in your lungs and can make people sick years after the fact."
And what about Parkinson's?
Darweesh: "There are three main environmental factors involved: the pesticides we still use in the Netherlands, fine particulate air pollution and solvents."
So what are you ultimately aiming for?
Darweesh: "We hope prevention will ultimately reduce the incidence of diseases like Parkinson's. If we can achieve that through our research, we'll be making a real impact." Peters agrees. "I hope we can eventually prevent all preventable diseases. All diseases caused by occupational exposure."
What does Lexces do?
The national Expertise Centre for Substance-Related Occupational Diseases (Lexces) pools knowledge and expertise on hazardous substances and occupational health risks. Board members include Dick Heederik, professor of Health Risk Analysis at Utrecht University (chairman) and Roel Vermeulen, professor of Environmental Epidemiology and Exposome Analysis (Utrecht University and UMC Utrecht). Susan Peters is deputy board member and, like Heederik, was appointed a member of the Occupational Disease List Advisory Committee by the Minister. Also see: www.lexces.nl