From the Chronicle:
The agency’s newly proposed rules took note of the [AFT's] explanation of how, typically, an instructor works at least three hours a week for every credit hour taught. By that formula, an adjunct who teaches four three-credit classes would be considered full time under the new legislation.
And hence would be eligible for health care. But watch out for the iron law of unintended consequences:
But even as the IRS is working to provide colleges with the guidelines they have sought from the agency, a few institutions have made pre-emptive moves by cutting back the number of hours adjuncts are allowed to work …