An Iowa farmer is leading a nationwide class-action lawsuit against the manufacturers of a commonly used weed killer linked to Parkinson’s disease.

It is one of a spate of class-action claims filed in just the past two weeks against the makers and distributors of Paraquat, a herbicide banned by China and many other nations but still legal to sell and use in the United States.

The Iowa case was filed May 3rd in U.S. District Court for the Southern District of Iowa on behalf of Doug Holliday, who farms thousands of acres near Greenfield in Adair County. Holliday has allegedly been using Paraquat on his ground crops since the 1990s. On behalf of himself and other farmers who have used Paraquat, he is suing the companies Syngenta and Chevron for manufacturing and selling Paraquat in Iowa and throughout the United States.

Paraquat is a synthetic chemical compound used since the mid-1960s as a weed killer, although the lawsuit alleges it is “the most highly, acutely toxic herbicide to be marketed over the last 70 years.” Paraquat is banned in more than 30 countries, including nations within the European Union, and in China, which is not known for an aggressive regulatory stance on health and environmental issues.