Compared with no exposure, herbicide exposure carried the highest pooled estimate at about 70 percent, while exposure to either insecticides or fungicides was associated with roughly a 60 percent increase. High pesticide exposure was associated with a near tripling of risk compared with no exposure, based on three studies, while lower exposure was associated with a doubling. Other research has separately linked ALS risk to workplace exposures including metals, particularly lead, and solvents, which complicates any attempt to isolate pesticides as a single culprit. The researchers did not establish that pesticide exposure causes the disease. The research examined occupational exposure, meaning sustained workplace contact.