SAGINAW, Mich. (AP) -- About 2,000 people who live along the Tittabawassee River may jointly sue Dow Chemical Co. for damages related to dioxin contamination in the area, a judge ruled Friday.

Saginaw County Circuit Court Judge Leopold P. Borrello ruled that lawyers for seven plaintiffs will represent all residents within the river's 100-year floodplain in a class-action lawsuit.

The seven plaintiffs are among 170 who have sued the Midland-based chemical company claiming that it polluted the river with dioxin, a chemical linked to cancer, birth defects and other problems.

Scot Wheeler, a spokesman for Midland-based Dow, said the company disagrees with the ruling and will appeal to the state Court of Appeals.

Dioxin is a persistent and toxic chemical that was a byproduct of Dow processes dating back several decades. High levels of dioxin have been found along the river near Dow's plant in Midland.

In his opinion, Borrello said that without a class-action suit, the court could wind up with 2,000 individual claims.

"Almost identical evidence would be required to establish negligence and causal connection between the alleged toxic contamination and plaintiff's damages," he wrote.

But Wheeler said class-action status should not have been granted because there are vast differences between the property owners, including their proximity to the river, dioxin levels on their land, current use of the property and when it was purchased.

Residents within the floodplain don't have to do anything to become part of the class-action lawsuit. They will be notified about it and about the procedure to exclude themselves, if desired.