Living next to croplands tied to greater ALS risk, younger onset age
Study finds disturbing trends near crop farms and vineyards, and over time
Living next to arable cropland significantly raises the risk of developing amyotrophic lateral sclerosis (ALS), according to a new study in northwestern Italy.
A significantly younger age at disease onset also was seen among those living near such farmland, which may include fields of cereals (wheat and barley), beans, and root crops (potatoes), and for those living for long periods near vineyards.
Findings suggest that environmental contaminants used in agriculture can be possible risk factors for ALS.
The study, “Croplands proximity is associated with amyotrophic lateral sclerosis incidence and age at onset,” was published in the European Journal of Neurology.
Study into environmental risks by type of agricultural land exposure
Exposure to certain chemicals in the environment, particularly pesticides and heavy metals, has been linked to an increased risk of developing ALS. People with ALS often have elevated levels of organic pollutants, especially pesticides, in their blood than those without ALS, and such pollutants have been associated with poorer survival rates.
Many studies have investigated the relationship between ALS, rural living, and occupational exposure to pesticides in agriculture.
Scientists based at the University of Turin decided to go one step further, assessing ALS risk among those living near different types of agricultural crops. Specifically, they collected 20 years of residential histories from ALS patients diagnosed between 2007 and 2014, enrolled in the Piedmont and Aosta Valley Registry for ALS, a database covering those regions in northwestern Italy.
“We evaluated the effect of residential proximity to different agricultural crops on ALS incidence … focusing on age at onset, site of onset and progression rate,” they wrote.
Farmlands included those growing arable crops — plants such as cereals (wheat and barley), beans, and root crops (potatoes, beets, carrots) — as well as vineyards, meadows, orchards, vegetable crops, nurseries, and paddy fields with semiaquatic crops (rice).
Analyses showed a rising incidence of new ALS cases in areas with more arable crops. The number of cases per 100,000 people per year steadily rose from 0.75 in areas with no arable crops to 1.81 when arable crops covered 60% of the land. Living next to fields growing other types of crops did not associate with an increased ALS risk.
ALS onset a median of 3.4 years earlier when living close to arable crops
Age at ALS onset also was significantly lower in people exposed to arable crops, either at diagnosis or using historical residence data. Compared with unexposed patients, the median age of onset was 1.8 years younger among those who lived within 1,500 meters (about one mile) of arable crops, and 3.4 years younger within 1,000 meters (0.6 miles).
A trend toward a similar risk was seen for patients who lived next to vineyards at diagnosis, but it only reached statistical significance with lengthy residence there.
“These results, considering that in the historical analysis we took into account crops proximity roughly between 1985 and 2015, can be related to a better classification of real patients’ exposure, especially considering that pesticide use has greatly changed over time,” the researchers wrote, adding that “arable crops and vineyards cultivation shared some common pesticide categories, mainly herbicides.”
ALS progression rate, as indicated by the Revised ALS Functional Rating Scale (ALSFRS-R) score, was similar regardless of cropland exposure. Still, ALS progressed more slowly at diagnosis for those living within up to 1,000 meters of vegetable crops, 2,000 meters (about 1.2 miles) of meadows, and 1,500 meters of nurseries.
Importance of exposure to farming contaminants, especially over years
Lastly, researchers conducted a subgroup analysis using historical data from patients without ALS-associated genetic mutations. Here, the median age of onset for men living within 1,500 meters of arable crops was up to 3.7 years earlier, and for men living within 2,000 meters of vineyards, it was up to 2.5 years younger.
These results “highlight the importance of weighting for potential environmental exposures to crop-related contaminants, and in particular considering historical residential exposure,” the scientists wrote.
“Future research is needed to clarify the possible causative role of specific environmental contaminants, pinpointing their biological neurotoxic mechanisms and reducing their detrimental effect through prevention or development of new-targeted drugs,” they concluded.
About the Author
