Researchers are taking a closer look at whether hidden hazards woven into modern life may be contributing to a rise in deadly ALS cases across the United States, as concern grows over diagnoses in young, fit and seemingly healthy men.
In 2022, roughly 33,000 Americans were living with the devastating neurological disease, also known as Lou Gehrig’s disease, according to the national ALS Registry.
By the end of the decade, that figure is projected to rise to more than 36,000.
An aging population accounts for part of the increase, but specialists say it does not fully explain a pattern that has become harder to ignore: more cases appearing among athletes, military veterans and otherwise healthy men who have no known genetic connection to the disease.
The issue drew fresh attention this week after former NFL star Chris Johnson, 40, revealed his diagnosis. At the same time, scientists are examining whether aspects of modern living — including physical trauma and exposure to chemicals at work or in daily routines — may be playing a role.
“Smoking, military service, certain occupational exposures such as lead, pesticides and solvents, and repeated head trauma have been linked with higher ALS risk,” board-certified neurologist Dr Rab Nawaz Khan told the Daily Mail.
Recent research from the University of Michigan has also pointed to possible risks tied to everyday leisure activities, including gardening and golfing, with scientists suggesting that exposure to pesticides and lawn-care chemicals may be a factor.
Taken together, the findings have intensified a pressing question for doctors and researchers: what is truly behind the rise in ALS?
Former NFL star Chris Johnson, 40, revealed his ALS diagnosis this week during an interview with Good Morning America
Johnson on the field during a Tennessee Titans game in 2013. The star was diagnosed with ALS in 2025 when he was 39
Outdoor hobbies
The 2024 study by the University of Michigan found golfing was associated with a threefold increase in risk, while gardening and yard work were linked to a 71 percent rise.
Woodworking has also been flagged, potentially due to exposure to chemicals such as formaldehyde.
Experts believe the link – which is particularly strong in male patients – may come down to repeated exposure to toxic substances. ALS attacks the nerve cells in the brain and spinal cord that control movement, and once these cells are damaged, they cannot be repaired. Over time, this severs the connection between the brain and muscles, causing them to weaken, waste away and eventually stop working.
Scientists suspect that pesticides, solvents and other chemicals may gradually damage these vulnerable nerve cells – either by triggering inflammation or by causing a build-up of toxic proteins in the body.
‘There are environmental toxins that have been connected to ALS through epidemiological studies,’ Dr Kuldip Dave, who oversees the ALS Association’s research program, told the Daily Mail.
‘So when you think about something like golf, or people living near farms, it’s possible that pesticides, insecticides, herbicides or other toxins could have an impact on the risk of developing ALS.’
While experts stress it is far too early to tell people to give up these hobbies, efforts are underway to identify risk factors that could be modified.
Physicist Stephen Hawking, who defied the odds after being diagnosed with ALS at 21 and living with the disease for more than 50 years. He died in March 2018
The number of estimated ALS cases in 2022 was 32,893, according to the national ALS Registry. By 2030, projected cases increase more than ten percent to 36,308
Toxic jobs
Certain professions have long been linked to a higher risk of ALS – particularly those involving intense physical labor or exposure to hazardous substances.
Researchers point to prolonged contact with workplace toxins, including metal particles, welding fumes, solvents, pesticides and industrial chemicals.
Manual and trade jobs consistently show elevated risk, with higher rates reported in manufacturing and chemical industries.
Construction workers and carpenters may face up to twice the risk, and are more likely to develop a form of the disease that affects speech and swallowing early.
A 2022 study in International Archives of Occupational and Environmental Health, involving 381 ALS patients and 272 controls, found sufferers reported significantly greater exposure to workplace hazards including metals, particulate matter and diesel exhaust.
Metal exposure showed the strongest link, increasing risk by 48 percent. Particulate matter raised risk by 45 percent, volatile organic compounds by 22 percent, and combustion and diesel exhaust by 20 percent.
Among specific exposures, iron and welding fumes carried the highest risks. Painters are also considered vulnerable due to volatile organic compounds (VOCs) in paints, solvents and thinners.
A still from the Good Morning America segment about Johnson and his ALS diagnosis
Football and head trauma
Professional athletes – especially football players exposed to repeated head trauma – appear to face a significantly higher risk of ALS.
‘Repeated head and neck impacts may be one relevant exposure in some professional contact-sport athletes, but they do not explain most ALS cases,’ Khan said.
A 2021 study in JAMA Network Open, analyzing more than 19,000 former NFL players, found they were nearly four times more likely to develop and die from ALS than the general population.
‘And most of those NFL players were in their mid-30s at the time of diagnosis, just like Chris,’ Dave said.
‘While that study didn’t look directly at risk factors, the obvious explanation is head trauma.’
Those diagnosed had played an average of seven years, compared to four and a half among those without the disease.
Earlier research has also pointed to head injuries more broadly. A 2007 study found people with multiple head injuries had a threefold higher risk, rising to an 11-fold increase for repeated injuries within a decade.
A meta-analysis of eight studies reported a 1.7-fold increase in risk among those with a history of head trauma.
British rugby player Rob Burrow during a match in 2010. He was diagnosed with ALS in 2019 at 37 years old, and died in 2024 at 41
Rob Burrow with his wife, Lindsey Burrow, and friend Kevin Sinfield in 2024
The role of intense exercise in ALS remains controversial, but growing evidence suggests it could have an impact in some cases. A 2023 review of 93 studies found frequent, strenuous activity may be linked to a higher risk.
In particular, researchers pointed to anaerobic exercise – short, high-intensity bursts such as sprinting or heavy weightlifting – as a possible factor.
Higher rates of ALS have been reported in elite athletes, including footballers, soccer players and cross-country skiers. Experts say this may reflect a combination of extreme training loads, repeated physical stress on the body – and, in contact sports, possible head impacts.
Scientists believe the link, if it exists, comes down to how intense exercise affects the body at a cellular level.
Heavy exertion can increase oxidative stress – a type of damage to cells – and place strain on motor neurons. Over time, this may accelerate disease in vulnerable individuals.
Crucially, the risk does not appear to apply to everyone. ALS is strongly influenced by genetics, with more than 40 gene variants implicated. Researchers think intense exercise may act as a trigger in people already predisposed, rather than a direct cause of the disease itself.
Experts stress that for the vast majority of people, exercise remains safe and beneficial, and the findings should not deter normal physical activity.
‘There may be some increased risk in some sports, but not enough that I would tell someone not to play,’ Dr Jeffrey Rothstein, a neurologist at Johns Hopkins, told the Daily Mail.
Smoking
Smoking is one of the more established lifestyle risk factors for ALS.
Scientists believe it may damage motor neurons directly or accelerate cellular stress that contributes to the disease, although the exact mechanism remains unclear.
A 2011 analysis published in JAMA Neurology, pooling data from more than 1.1 million people, found smokers had around a 40 percent higher risk of developing ALS than non-smokers.
More recent research has reinforced the link. A 2024 meta-analysis of 32 studies found smokers had an overall 12 to 14 percent increased risk, rising to 28 percent among current smokers.
The association appeared strongest in women, with a 25 percent higher risk, while no clear link was found in men – potentially because these men are more exposed to other risk factors such as workplace toxins.
Crucially, smoking is one of the few risk factors people can control. Khan’s advice is simple: ‘Avoid smoking.’
Eric Dane, best known for his role as Dr Mark Sloan on Grey’s Anatomy, attends a premiere in June 2025. He was diagnosed with ALS in 2024 at age 51
Dane leaves Toronto International Airport in October 2025. The actor became an advocate for ALS awareness before he died in February
Diet and metabolism
Diet is a far less certain piece of the puzzle, but researchers believe nutrition and metabolism may still play a role in risk and progression.
Oxidative stress and inflammation – both influenced by diet – are thought to contribute to nerve cell damage.
Some studies have linked diets high in processed meats to poorer outcomes, while high-carbohydrate, low-fat diets have also been associated with increased risk.
Environmental toxins may also enter the diet. Certain seafood can contain BMAA, a toxin produced by blue-green algae, or elevated levels of mercury.
On the other hand, nutrients with antioxidant and anti-inflammatory properties appear protective.
Higher intake of vitamin E, omega-3 fatty acids and carotenoids has been associated with lower risk, while a 2024 genetic study linked oily fish, coffee and fresh fruit to reductions of 24, 26 and 38 percent respectively.
However, experts stress the evidence remains limited.
‘Dietary risk factors are really tough to confirm and validate,’ Dave said.
‘I think from a risk factor standpoint, there’s less certainty on that one.’
He added that while healthy eating is always advisable, particularly after diagnosis, its role in preventing ALS remains unclear.
Former NFL star Johnson is far from the only famous face to confront ALS. Stephen Hawking, the brilliant physicist, defied the odds after being diagnosed at 21, living with the disease for more than 50 years and becoming a global icon of resilience. He died in March 2018.
Actor Eric Dane, known for his role on Grey’s Anatomy, revealed his diagnosis in 2024 at age 51. He became an advocate for ALS awareness until he died in February.
In the UK, rugby stars Rob Burrow and Lewis Moody, both World Cup winners, were diagnosed with ALS within years of each other. Burrow died in June 2024.
