Marrero has become a fierce advocate for patients.

In his January 2023 letter, he wrote to Canada’s top public health official and to Russell warning them the number of cases has grown from 48 to more than 147, claiming that some are as young as 17 years old.

He wrote that some patients are experiencing “very advance evidence of neurodegenerative diseases,” including dementia, severe pain syndrome, brain and muscle atrophy and more.

“Some of these patients are, unfortunately, in advanced stages of clinical deterioration and near the end of life,” he wrote.

He also warned that some patients’ blood work showed elevated levels for compounds found in herbicides such as glyphosate, and said more testing should be done to rule out environmental toxins, including the neurotoxin BMAA, which is produced by blue-green algae.