The Occupational Safety and Health Administration ignored at least four internal scientific studies warning of an increased risk of cancer to workers exposed to the chemical formaldehyde, the United Auto Workers and the American Public Health Association have charged in a suit filed in U.S. District Court here.

Instead, OSHA declined to reduce formaldehyde exposure and justified its action by citing another study that wasn't complete at the time, according to documents filed with the court.

The suit argues that in 57,000 workplaces, 1.4 million employes "face a risk of cancer and other adverse health effects" under the present OSHA standard.

The suit alleges that OSHA administrator Thorne Auchter did not rely on the "best available evidence" early last year when he refused to impose an emergency formaldehyde regulation the UAW sought. The suit asks for a stricter standard.

OSHA spokesman Douglas Clark said last week that "there is just no evidence then or now that an emergency exists" regarding formaldehyde. He also denied the suit's allegation that top OSHA officials maintained periodic contact with industry attorneys but refused information from the UAW and other unions in reaching its decision.

Clark also said it was not important that in refusing to set stricter standards the agency relied on a staff study that was incomplete. "The agency still does not have enough data to put formaldehyde" on its agenda for possible further regulation, he said.Equality Day Sows Problems at USDA

Friday was Women's Equality Day at the Agriculture Department, just as it was throughout the federal establishment, and it probably couldn't have come at a worse time.

As controversy swirled over the Reagan administration's handling of women's issues, USDA gussied up the main patio at headquarters to highlight feminism in farming. Many of the posters actually highlighted men. A feature was an enlargement of President Reagan's Equality Day proclamation. One display stressed jobs for home economists. Another, from a division in which women work side by side with men, featured two deceased women scientists as its paragons.

One awe-struck veteran male bureaucrat said, "They've got 364 days of the year to promote home-economist jobs. So this is the one day of the year you don't do it. But do they get the message? No."