Beginning about 18 months ago with the recall of 15,000 glazed ceramic casserole dishes from the shelves (and the catalogue) of Williams-Sonoma, public concern has veered toward the dangers of this kind of cookware.

Produced in Mexico, Italy, Portugal and China among other countries, glazed ceramic pieces come in the form of plates, bowls, gratin dishes, pitchers and mugs as well as casserole dishes. Some of them are brightly colored, some of them plain.

The problem with the Williams-Sonoma pieces and others was the presence of lead in the glazes. The lead can leach into foods cooked, stored or served in these dishes and from there get into the human body, where it causes all kinds of problems, some of them very serious.

A partial list of these problems, according to the Food and Drug Administration: possible harm to the liver, kidneys, and to the nervous, cardiovascular, immunologic and gastrointestinal systems, as well as learning and behavioral disorders in children. When these problems show up they are often difficult to diagnose, since lead poisoning is not first on every physician's list of suspects.

Most glazed ceramic pots are not poison. Of 339 samples tested by the FDA during the last fiscal year, 4.4 percent were found to have unacceptable levels of lead. None of the 4.4 percent was manufactured in the United States. Samples from Italy, Hong Kong, the Netherlands, China, Morocco, Portugal, Puerto Rico, Spain and Thailand, however, did have problems.

The problem for consumers is that it's impossible to tell the good glazes from the bad just by looking at them. Lead adds the shiny, glossy look to glazes, but artisan potters and manufacturers can achieve the gloss without the lead. To add another layer to the problem, cadmium, another toxic metal, is frequently used in glazes too. It brings up bright colors in decorated pottery.

And there's nobody who can do all the sifting for us either. Although the FDA has established standards for lead levels and does spot check ceramic ware manufactured in this country and that imported from abroad, it can't test every single pot. And pots bought in foreign countries by tourists are difficult to check at all.

Williams-Sonoma ran into trouble with casseroles imported from Spain, but the products of other countries are being watched carefully as well. FDA says it's now giving higher inspection priority -- meaning its people think they have more reason to be suspicious -- to ceramic ware coming from India, Italy, Macao, Mexico, North Korea, Pakistan, the People's Republic of China and Thailand.

For the most part, retailers are as anxious as consumers about selling dangerous ceramic pots. Many stores run their own tests on pottery they buy from wholesalers. But there is sometimes a gap between the time the pots (or plates or pitchers) go on the shelves and the time they're found to be troublesome. Meanwhile, cooks may be buying potentially dangerous cookware.

And, outside the normal retail transactions, ceramic pots float all over the place. A friend recently bought one -- a pretty Mexican casserole -- at a yard sale. Other friends have inherited various pieces or brought them back from vacation trips.

What should you do about pots you own?

If there's any question about their glazes (artisan potters will be able to tell you whether they've used lead glazes or not, and the vast majority do not) don't use the pot for cooking or storing food, especially acid foods. Acids tend to increase the amount of lead leached from the glaze into the food. And the longer the food is in contact with the glaze, the more lead is leached.

While there are now federal standards for acceptable levels of lead, there weren't always. (And even now it's possible that some could slip through spot checks.) So don't use antique or old pots, mugs, casseroles and so forth with food or drinks.

One final bright note: the popular brown, glazed French Provenc al pottery sold in the form of gratin dishes, pitchers, casseroles and terrines, and used widely in restaurants and homes here and in France, has never been found to contain lead