"IF YOU'RE BLACK and live in D.C., you're a high cancer risk. Very high." This public service ad is broadcast daily over four local television stations and several radio stations. It's repeated in placards posted in the Metro system. It's wholly well-intentioned. It's also misleading and slightly offensive. The ads ought to be dropped. There are better ways to deliver the message.

The American Cancer Society composed these ads in an effort to alert blacks to the dangers of the disease. For some time physicians have noted that cancer mortality rates among blacks are rising dramatically, and the Comprehensive Cancer Centers at Howard and Georgetown universities have conducted studies showing that the mortality rate for blacks in Washington is higher than in any other major city. The rasons are not entirely clear, but they evidently involve high consumption of tobacco and alcohol, certain dietary habits and unawareness of cancer's symptoms.

The dangers are real, but they are the same dangers that confront everyone. The trouble with the ads is that, in their zeal to catch the attention of blacks, they seem to suggest that there is something about one race, and something about the city, that contributes to the risk of cancer. They leave an implication -- unintended, but strong -- that all blacks are more likely to contract the disease. There's no evidence of that. While rates are extremely high among black men, for example, the rate among black women is lower than the average for whites. To some listeners, particularly children, the ads seem to strengthen the impression that the disease is not only racial in pattern but perhaps hereditary, or contagious.

The cancer society has achieved some gains through these ads, in calls from people seeking information and referrals. But it found in a study several years ago that blacks get tests and physical checkups nearly as often as the population at large. It's better and more effective for the cancer society to address everybody, without racial reference, when it carries on the exceedingly valuable work of telling the world about early warning signs, and about the dangers of certain habits -- starting with smoking.