ADVOCATES FOR FARM workers were disappointed by Labor Secretary William Brock's decision to delay by at least 18 months a federal requirement that field workers be guaranteed access to clean drinking water, toilets and a place to wash their hands. Their disappointment is easy to understand. Still, measured against the sorry record of this country's treatment of the people who harvest its produce, Mr. Brock's decision must be viewed as potential progress.

For more than a decade, the farm workers' advocates have been fighting for recognition that they, no less than all other U.S. workers, are entitled to modest protections for their health and self-respect. Field workers, however, are sadly lacking in political clout -- while their employers have a great deal -- and successive administrations have found reasons to ignore their concerns even while adding to the protections already provided more powerful labor groups.

The most severe setback occurred earlier this year, before Mr. Brock took over the department. Robert Rowland, the since-departed administrator of Occupational Safety and Health programs, decided not to issue any federal rule at all. Mr. Rowland reasoned that farm workers were already adequately protected by the rules that 13 states with large numbers of farm workers have enacted. He didn't explain why so many credible studies demonstrated that severe health hazards remain, or why, if existing rules were already so strict, farm owners were so concerned about having to meet minimum federal requirements.

Secretary Brock, however, has read the evidence more accurately and agrees that current protections are far from adequate. Most states have no rules at all, and many that have rules don't enforce them. But he is still willing to give the states another 18 months to act before deciding that a uniform federal rule is needed. Whether this approach is simply a way to sidestep a touchy issue or means real benefits for farm workers will depend on what happens next. The setting of a deadline for state action and the threat of a federal rule are certainly much better than a decision not to have any rule at all. Aides to the secretary also say that he is firmly committed to seeing that states make real progress -- not just in putting statutes on the books but also in seeing that things get better in the field. That will mean putting substantial resources to work with states and checking on progress -- and being ready 18 months from now to take decisive action if the states have failed to meet the test.