Last night I had a dream: I dreamed that the children singing in the buses were doing it because they loved art. Fragment in a mural denouncing unemployment.

Murals have been called the notebooks of the poor. In underdeveloped areas, walls are a place where the voiceless can tell their stories of anguish, injustice, and disease. But more than just recording their lives and struggles, murals are an effective way to communicate with the rest of the city. In many places, murals are illegal and have to be painted under the cover of night. Some cities, however, have walls unofficially designated for these expressions.

Most murals are political, defending the right of workers, protesting the price of bread, or backing a fringe party with no money. Recently, there's been a trend to paint highly fanciful images of alienation, despair, indifference to politics, and the corruption of urban life.

These are painted by muralist clubs or brigades, usually young people from the marginalized parts of town, who go out into the city to spread their messages of nihilism, heavy metal, and disaffection.

But alongside these, a new type of mural is appearing with increasing frequency: murals that alert the public to the dangers of drugs, infectious diseases, sexually transmitted diseases, pollution, television, and even the existential void, which is the result of a dissipated and uncommitted life. They disseminate the message that redemption is possible through commitment to people, healthy lives, and a respect for design and form.

The most remarkable thing about these murals, painted in stealth and darkness, is the variety of forms and styles. In a visual language that is accessible to all, they bluntly show the hazards of smoking coca paste, Latin America's equivalent of crack; the perils of alcohol; and the dangers of unprotected sexual encounters that can lead to pregnancy, AIDS, and other STDs.

These muralist brigades are creatively supplementing the work of health ministries, whose information campaigns belong to the formal sector, since they are planned and staffed and have budgets for their execution. The work of these anonymous budding artists, on the other hand, reflects a personalized agenda whose fresh, savvy approach undoubtedly is more spontaneous.

Maybe the two forces for change would do better by coming face to face, joining hands, and sharing their respective expertise. That would bring more power to the people from two very reliable sources.