Canadian Occupational Safety

AUGUST/SEPTEMBER 2017 23 Workers are most commonly exposed when the chemicals are in storage and during application. Pesticides can enter the body by ingestion, inha- lation or skin absorption. When using pesticide products, check the label and the safety data sheet for the required personal pro- tective equipment (PPE). This may include chemical resistant unlined gloves and footwear, a long-sleeved shirt and long pants, socks, a res- pirator and eye protection. Studies have shown that wearing chemical resistant gloves and footwear can sig- nifi cantly reduce exposure, says the Canadian government. VIBRATION Teschke and Harris' study found agricultural workers had "consis- tent, signifi cant increased odds" for developing Parkinson's, but pesticide exposure did not come out as the defi nitive cause. This led Teschke and her team to take look at other possible causes and they came up with whole body vibration, which occurs as the body rests on a vibrating surface, such as vehicles and heavy equipment. "A good example is farmers. You get a subtle amount of vibration just driving on the road and you can get more dramatic vibration as you go off road and drive different kinds of equipment that has less suspension and then you can get these very dra- matic shocks when you hit a pothole or, in the case of farming, probably every few feet," says Teschke. The researchers were interested in this as a potential occupational exposure because the mechanical stress of vibration and associated shocks could be similar to the stress precipitating a head injury. They asked study participants to report their occupational use of vehicles and then they identifi ed the level of vibration intensity for each piece of equipment. They found an interesting U-shaped effect where the risk increased with no exposure but also with increasing intensity of exposure. While the results are a bit tricky to interpret, they certainly warrant fur- ther study. "These higher intensity vehicles are the ones that are associated with physical shocks — lots of bumps and high amplitude of exposure — and potentially repeated shocks could engage some neuroinf lammation mechanisms," says Harris. "This is the big area of interest in Parkinson's disease etiology now, so it would be great to test that directly." MANGANESE Manganese exposure is another potential occupational risk factor for Parkinson's-t y pe symptoms that has been hotly debated. Some studies show an increased risk, while others show a decreased risk or no association. Manganese is a common compound in welding fume. "We are aware of various studies that have been done in this area but we are not 100 per cent sure how conclusive those studies are," says Dan Tadic, executive director of the Canadian Welding Association in Milton, Ont. "Even some of the studies that I have seen, there are some question marks." In 2013, the ACGIH lowered its TLV for manganese from 0.2 milligrams per cubic metre (mg/m3) to 0.02 mg/ m3. A review of studies over the pre- vious 15 years indicated effects to the central nervous system occur at expo- sure levels below 0.2 mg/m3. When the change was made, the Canadian Welding Association com- municated this to its members and conducted events to raise awareness. While ACGIH limits are often adopted by Canadian jurisdictions and made law, the vast majority haven't quite gotten there yet. Only Nova Scotia, Newfoundland and Labrador, P.E.I., Manitoba and the Labour Program (for federally regulated workplaces) have accepted the new TLV because their OHS regulations say to refer to the latest version of ACGIH limits. The majority of the provinces and territories are still using the old 0.2 mg/m3 TLV. This is of concern because a recent study found signs of Parkinson's disease showed up in welders with an estimated exposure of only 0.14 mg/ m3. The study, released in December from the Washington University School of Medicine in St. Louis, Mo., found the more workers are exposed to manganese-containing welding fumes, the more quickly their symptoms of parkinsonism progress. Exposure was most strongly asso- ciated with upper limb bradykinesia (slowness of movement) upper and lower limb rigidity and impairment of speech and facial expressions. Welders who worked in confi ned spaces appeared to have particularly marked worsening of parkinsonism. Overall, the study found the preva- lence of parkinsonism was 15.6 per cent in welding-exposed workers, demonstrating a "high prevalence of parkinsonism" compared to non- welding-exposed workers. According to Tadic, there are a vari- ety of controls employers can put in place to reduce welders' exposure to manganese fumes: • use welding consumables (such as wires) with lower manganese levels • use lower welding voltages • use ventilation equipment to exhaust fumes • use newer welding technology, such as pulse welding, which generates less fumes than any other semi-automatic welding process • use appropriate respiratory protection. Manufacturers have made many improvements over the years when it comes to reducing the amount of manganese used in steel, but the industry has certainly been grappling with this issue, says Tadic. "Imagine how much steel is used in today's bridges and pipelines and all the machinery that is being made, buildings and automotive industry and a variety of applications. If you were to eliminate (manganese) com- pletely, you would drive the cost of these alloys through the roof and cause all kinds of serious damage to the economy," he says. Teschke's study found welders had an elevated risk for Parkinson's as did heavy equipment operators, farmers, carpenters, gas station workers, and perhaps a bit surprisingly, science, law and library jobs. The latter may be due to the fact that infl uenza is associated with an increased risk of Parkinson's, says Teschke. "It's interesting because they show up as having an elevated risk but man- agement and administration doesn't. If you think of one of the biggest dif- ferences between those groups, it's their interaction with people. Social sciences, and a lot of those folks, a lot of them are people who interact with a wide swath of the public in their regular work life, so they have more potential to be exposed to the fl u." To this end, employers would be wise to promote good health and handwashing in the workplace, espe- cially during fl u season. While the theories vary and some- times contradict each other, the one thing researchers can all agree on when it comes to Parkinson's is how diffi cult it is to fi gure out if there is a relationship. That's why the best bet is to apply the precautionary principle, says Teschke. "The biggest surprise to me when I started in this fi eld was how little we know about so much," she says. "To the extent that you can offer your employees a very clean, low exposure to either injury risk or chemical expo- sure risk, if you can give them that, that's a positive in ways you may not know that you'd hate to fi nd out in the future." 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