ALS environmental factors

ALS Environmental Factors

There is a lot of ongoing research into amyotrophic lateral sclerosis and it is helping us all to better understand the disease and what it means for those who have been diagnosed with it.

ALS, for example, has a genetic component. Epidemiological studies show us what factors are putting us most at risk, the extent of the disease and which demographic groups it affects.

The biggest mystery surrounding ALS, however, seems to be what actually causes it. A lot of different work has gone into finding connections related to ALS and there is still a lot that needs to be discovered.

Here we take a much closer look at whether there are environmental factors such as smoking and toxins or pesticides in the environment that may make it more likely for people to be diagnosed with ALS if they are exposed to them.

In many diseases around the world, environmental factors play a role, whether it’s in causing illness or being a contributory factor.


Man smoking cigarette
Recent research suggests there may be a link between smoking and ALS

We all know that smoking is unhealthy and it is associated with a wide range of diseases, most notably lung cancer. Research suggests that this habit may also be an ALS risk factor. A study in 2011 involving over a million people found that ALS was 42-44% more likely to occur in those who smoked than those who didn’t.

Previous studies involving smoking had shown some promising results but there was also contradictory research that said there was little or no association.


Most of us don’t understand much about toxins but they may also be a factor in ALS. Heavy metals such as lead and mercury can find their way into our water supply or be present in certain occupations. Liquids such as solvents are other toxic materials that we are often exposed to in life.

The evidence here is quite unclear, with some studies showing an association whilst others only have a weak one at best.


We tend to think of exercise as good for us, and rightfully so. There’s no doubt that there are numerous benefits of regular exercise when it comes to healthy living.

We do know that the type of exercise that is undertaken following a diagnosis of ALS is important, but is there evidence to suggest that it can actually contribute to the development of the disease in the firs place?

Research in the Netherlands found that ALS risk factors increased with more strenuous exercise. 1,500 adults diagnosed with the disease were questioned and the results were statistically significant.

What the exact connection is and how this mechanism works is still unclear but it’s a research finding that has been replicated in other studies.

Beta-methylamino-l-alanine (BMAA)

ALS is prevalent in certain places such as Guam in the Pacific. BMAA is a protein that is produced by bacteria in the diet of the people and has been shown to damage motor neurons. Whilst this may be the reason for the prevalence of ALS in Guam, it doesn’t also mean that this is the only cause.

There are likely to be numerous causes for the disease and its development can depend on a variety of different circumstances.


There are about 320,000 different viruses that affect mammals in the world today. Some, like polio, we have largely managed to eradicate. It seems sensible, therefore, to ask if ALS can be caused by a virus.

Unfortunately, there is not much evidence currently supporting this hypothesis. Whilst there has been some interesting work involving retroviruses, it’s unlikely that this is going to be a fruitful avenue of investigation in the future.


Military soldier
Research also suggests there may be a link between the military and ALS

It might sound odd to mention warfare when it comes to a disease such as ALS, but research involving veterans has found there may indeed be a causal link. Some of the evidence points to the fact that it doesn’t matter which branch the individuals were in.

There may be some crossover with other environmental factors here, particularly physical exercise. Those training in the army often have to perform rigorous activities which may be the main reason why the prevalence is so much higher in this group of people.


A study involving 150 patients with ALS suggested exposure to pesticides may cause as much as a 5-fold increase in the disease. Whilst this evidence has not been widely replicated, it may explain why many people who went to war or joined the military are susceptible to ALS.

ALS risk factors are often difficult to identify. It’s challenging to try and confirm that an environmental factor is linked to a disease, especially when the general population is exposed to similar potential risks and do not develop it.

In truth, there may well be a range of different factors that affect someone’s susceptibility, including their own biology and family history.