HAUPPAUGE, N.Y. (AP) _ A law requiring rest breaks and special training for many workers using video display terminals went into effect today in a Long Island county despite a legal challenge.

Suffolk County health officials, who will enforce the law, estimated that it applies to 8,500 VDT users in 150 to 200 businesses.

The measure is believed to be the first VDT-regulating law enacted by a local government.

A state Supreme Court judge is expected to rule within the next two weeks on a challenge to the measure brought by four businesses.

The judge has already granted the four businesses a preliminary injunction blocking a section of the law that would have required employers to pay 80 percent of the cost of eye examinations and glasses for VDT operators.

Suffolk County's 18-member legislature approved the law in June over the objections of County Executive Patrick Halpin, who said it would hurt businesses and was of questionable value to VDT operators.

The measure applies to operators who spend more than 26 hours a week in front of a screen in a private workplace with 20 or more terminals.

Beginning today, those workers must be given a 15-minute break or alternate work assignment every three hours.

The employers also must notify VDT operators of health hazards, including eye strain and nervous disorders, which may result from prolonged use of VDTs, and must schedule training in recognizing symptoms and taking protective steps.

The law does not include fines for violations, but health officials can file civil charges to force compliance.