SAN JOSE — A judge has tossed a lawsuit filed against Monsanto Co. by the cities of San Jose, Oakland and Berkeley. The suit claimed that the St. Louis-based business is just as responsible as the cities for cleaning up harmful polychlorinated biphenyls, or PCBs, in San Francisco Bay.

U.S. District Court Judge Edward J. Davila, however, left the door open in his ruling Monday for the cities to amend and refile the complaint.

The suit contends that PCBs manufactured and sold by Monsanto between the 1930s and 1970s polluted and continue to pollute the bay through runoff, forcing the cities to spend money to reduce discharge of the chemical and comply with various regulatory requirements.

PCBs are known to cause a number of health issues, including cancer in humans, and destroys populations of fish, birds and other animal life. Finally banned by Congress in 1979, the chemical was used in a variety of applications, such as paint, sealants and lubricants.

One of the arguments made by the cities was that the PCBs generated by Monsanto constitute a public nuisance. Davila said the cities couldn’t prove their property was affected. The property, in this case, the contaminated stormwater, actually belongs to the state.

“The cities do not take ownership of stormwater merely because it flows through municipal pipes on its way to the bay,” Davila said.

Davila also rejected a claim in the suit that Monsanto is jointly responsible for the contamination of the bay because the cities have been required to spend money to reduce PCB levels.

“The cities have had to pay because of a regulatory requirement, not an adverse judgment,” Davila said.

Company officials welcomed the ruling.

“The court’s ruling confirms that there is no legal basis of the cities’ claims,” Scott Partridge, vice president of global strategy at Monsanto, said in a statement. “The cities of San Jose, Berkeley and Oakland have been ill-served by the overly aggressive tactics of their contingency fee counsel, and we hope this ruling will conclude this matter.”

The cities, however, are not ready to concede. An amended complaint will be filed by Sept. 13, the deadline set by the judge, according to San Jose city spokesman David Vossbrink.

Contact Jason Green at 408-920-5006. Follow him at Twitter.com/JGreenMercNews.