Fifteen Bethpage residents filed a $500 million class-action lawsuit this week against Northrop Grumman, claiming the defense contractor’s manufacturing operations exposed them to toxic chemicals in air, drinking water and soil.

The residents allege that Northrop Grumman did not properly warn the community about contamination generated on a parcel of more than 600 acres in Bethpage, where the company created, manufactured and tested airplanes and craft used in space exploration between the late 1930s and 1996.

Over the decades, residents were exposed to a number of toxics, including arsenic, cadmium, chromium, polychlorinated biphenyls and volatile organic chemicals that can cause cancer, according to the lawsuit filed Tuesday in state Supreme Court in Mineola.

“Defendants allowed or caused these ultra-hazardous and abnormally dangerous substances to leak into the surrounding land and groundwater, and in doing so, failed to warn plaintiffs of the dangerous condition that was caused thereby,” the lawsuit said.

Northrop Grumman spokesman Vic Beck, in a statement Thursday, said the company had not been served the lawsuit “but based on what we have been told about the complaint, the allegations appear to be entirely without merit.”

Northrop Grumman, he said, works “in close coordination with federal, state and local environmental and health authorities to address legacy environmental conditions and protect the residents in the Bethpage area.”

Grumman Aeronautical Engineering Corp., which became Northrop Grumman, operated on the site as a government contractor with the U.S. Navy, helping to build wartime planes, including the Hellcat, and later the Apollo Lunar Module.

Contamination in drinking water was discovered in the late 1940s. Volatile organic chemicals were detected in the mid-1970s, and the site was added to the state superfund list in 1983. Several groundwater plumes have been traced to the site, and one has stretched more than three miles from Bethpage.

The contaminated areas are subject to several cleanup plans, and the defense contractor and the Navy have been under increasing pressure from the state to remediate affected areas.

Local officials said the groundwater plumes put the drinking water supplies of 250,000 people at risk.

Attorney Hunter Shkolnik, whose Manhattan firm filed the lawsuit, said the 15 residents live at 10 properties in Bethpage. At each residence, he said, soil tests in March revealed elevated levels of contaminants. Those include the carcinogenic solvent trichloroethylene.

“The resulting exposure has significantly increased the risk of plaintiffs and the class contracting serious latent diseases, including but not limited to lung, skin, breast, bladder, liver, kidney and prostate cancer, permanent intellectual and behavioral effects on child development, effects on the central nervous system, respiratory, and other diseases and conditions,” the lawsuit said.

In addition to personal injury and property damage claims, the residents want Northrop Grumman to pay for a medical monitoring program to track the health of residents and research the effects of prolonged exposure to the chemicals associated with the site.

“We’ve suffered so much,” said Bella Kholodny, one of the plaintiffs. “It’s not over yet. I have cancer from this. My husband has cancer. Everybody has cancer.”

In tort cases alleging toxic damage, proving the cause and the source of a health condition can be difficult, said Edward Lloyd, director of the Environmental Law Clinic at Columbia Law School.

“One of the challenges for the plaintiffs will be to show that, in fact, the company caused harm to them,” he said.

Shkolnik said the contamination also has caused people to be concerned about their health, prevented them from enjoying their homes and damaged property values.

“It’s been this little dirty secret that people whisper about but nobody is stepping up to clean it,” he said. “We’re talking generations of families being exposed. The longer they’re exposed, the worse it is.”