A diagnosis of amyotrophic lateral sclerosis (ALS) can be devastating for the person affected and their family. It can also raise difficult questions about why the illness developed, particularly where someone spent years working with pesticides.
New research published in Occupational & Environmental Medicine in September 2026 adds to growing evidence of an association between workplace pesticide exposure and ALS. The findings are particularly relevant to people working in agriculture, horticulture, forestry, groundskeeping and other roles involving the regular use of pesticides.
What is ALS?
ALS is the most common form of motor neurone disease. It damages the nerve cells that control voluntary movement, causing progressive muscle weakness and loss of mobility.
The condition can eventually affect a person’s ability to speak, swallow and breathe. It progresses rapidly, and there is currently no cure.
For a person diagnosed with ALS, the physical, emotional and financial consequences can be profound. Family members may also have to take on significant caring responsibilities while dealing with uncertainty about the future.
What did the research find?
The researchers reviewed several earlier studies examining pesticide exposure and motor neurone disease. These included eight case-control studies reporting 1,734 cases and three studies involving a further 457 cases of unspecified motor neurone disease.
When the results were combined, the researchers found that:
- Any workplace exposure to pesticides was associated with a 60% higher risk of ALS compared with no exposure.
- High-level pesticide exposure was associated with almost three times the risk.
- Lower-level exposure was associated with approximately twice the risk.
- Herbicide exposure was associated with a 70% higher risk.
- Exposure to insecticides or fungicides was associated with a 60% higher risk.
- Men exposed to pesticides at work were twice as likely to develop ALS as men who were not exposed.
These figures describe relative risk. For example, a 60% higher risk does not mean that 60% of exposed workers will develop ALS. It means that the risk within the exposed group was 60% higher than the risk recorded in the unexposed group.
The finding concerning men was based on three studies that reported results separately by sex. It does not establish that women face no increased risk. It means that the pooled data available to the researchers produced a clear result for exposed men.
Does pesticide exposure cause ALS?
The research establishes an association between occupational pesticide exposure and an increased risk of ALS. It does not prove that pesticides caused the condition in every exposed worker who later received a diagnosis.
ALS is a complex disease. Its development may involve genetic, environmental and occupational factors. Researchers may also need to consider the specific chemicals used, how often exposure occurred, its intensity and duration, and the ways in which a worker came into contact with those chemicals.
Even with those limitations, the findings are significant. The researchers concluded that their review adds to the evidence that occupational pesticide exposure may increase ALS risk. They also called for measures to reduce workers’ exposure during pesticide use.
Which workers may be affected?
Pesticide exposure is often associated with farming, but it can occur across a wide range of occupations. Workers who may have experienced repeated or significant exposure include:
- Farmers, farm employees and agricultural contractors
- Horticultural and nursery workers
- Forestry workers
- Groundskeepers and greenkeepers
- Gardeners and landscape workers
- Pest-control workers
- Workers involved in storing, mixing, transporting or disposing of pesticides
- Employees who cleaned contaminated machinery, clothing or equipment
Exposure may occur while chemicals are being mixed, loaded or sprayed. Workers may also be exposed through leaks, spills, spray drift, contaminated surfaces or inadequately cleaned protective equipment.
A person does not necessarily need to know the precise name of every product used before seeking legal advice. Employment records, product labels, purchase records, safety data sheets, spraying logs and witness evidence may help identify the substances involved.
What duties do Irish employers have?
Under the Safety, Health and Welfare at Work Act 2005, employers must protect their employees’ safety, health and welfare at work so far as is reasonably practicable.
This includes identifying workplace hazards and carrying out a written risk assessment. Where employees may encounter pesticides or other hazardous chemicals, an employer should assess the nature, degree and duration of the potential exposure.
Depending on the work involved, appropriate precautions may include:
- Avoiding or reducing the use of hazardous substances where possible
- Choosing safer products or working methods
- Providing suitable spraying, mixing and ventilation equipment
- Supplying appropriate protective clothing and respiratory protection
- Ensuring protective equipment fits properly and is maintained
- Providing clear information, instruction, training and supervision
- Following product labels and safety data sheets
- Arranging safe storage, handling and disposal
- Maintaining washing and decontamination facilities
- Reviewing controls when working practices or scientific knowledge change
Personal protective equipment should not be treated as the only safeguard where exposure can be prevented or reduced through safer products, equipment or systems of work.
Could an ALS diagnosis lead to a workplace compensation claim?
A possible connection between ALS and occupational pesticide exposure does not automatically establish a legal claim. Each case must be assessed on its own facts.
A claim would generally require evidence concerning the worker’s exposure, the employer’s safety arrangements, any failure to take reasonable precautions and the medical connection between the exposure and the diagnosis.
This may involve examining:
- The products and active ingredients used
- The frequency, intensity and length of exposure
- How the chemicals were mixed, applied and stored
- Whether spills or incidents occurred
- What protective equipment was provided
- Whether training and safety information were adequate
- The employer’s risk assessments and safety statement
- The worker’s medical and occupational history
- Expert medical and scientific evidence on causation
The new research may form part of the scientific evidence considered in an individual case. It is not, by itself, proof that a particular employer caused a particular diagnosis.
Occupational disease cases can be complex because exposure may have occurred over many years or with several employers. Records can also become harder to obtain as time passes. Anyone considering a claim should seek legal advice promptly, as legal time limits may apply.
What should you do if you are concerned?
Your health and medical care come first. Speak to your treating doctor or specialist if you have questions about your diagnosis or whether occupational exposure may be relevant.
It may also help to write down what you remember about your work while the details remain available. This could include employers, job roles, dates, pesticide names, spraying practices, protective equipment and any occasions when you became soaked, inhaled spray or experienced a significant spill.
Keep any documents you still have, including training records, photographs, labels, work diaries, payslips and correspondence. Don’t put yourself at risk by returning to a workplace or handling chemical containers to obtain evidence.
We’re here to help
If you or a family member has been diagnosed with ALS and you believe workplace pesticide exposure may have played a part, you deserve clear and sensitive advice.
HOMS Assist can listen to what happened, review your work and exposure history, and explain whether there may be grounds to explore a compensation claim. We understand that this is an extremely difficult time. We’ll guide you through your options in plain language and at a pace that works for you.
Contact our specialist workplace accident claims team for a confidential consultation. We’re here to help you understand your rights and decide what to do next.
About the author: Sean Fitzgerald is a Partner at HOMS Assist with over a decade of experience in personal injury law, specialising in workplace accidents and industrial disease cases. Combining his legal expertise with a science background, Sean is renowned for securing justice for employees affected by employer negligence. His commitment to fairness and deep understanding of Irish workplace accident law are evident in his advocacy for injured workers.
*This article provides general information and does not constitute legal or medical advice. Research identifying an association does not establish causation in an individual case.
