The appeal of the downtown jewelry district long has been its historical buildings and deal-making wholesalers and retailers.

But history has caught up with the area -- bounded roughly by 5th and 8th streets, Grand Avenue and Broadway -- as environmental concerns saddle several building owners with expenses in upgrading their facilities.

Some of the cleanup efforts can be traced to two years ago, when state Attorney General Bill Lockyer put a halt to jewelry manufacturing in the Park Central Building on Sixth Street, citing unsafe levels of chemicals such as copper, chromium and lead.

Park Central was cleaned up, but fear of further crackdowns led to the formation of a neighborhood task force to address a variety of environmental regulations. About 30 buildings have since gone through clean-ups, with much of the work centered on ventilation.

"We wanted to keep the industry together without being so onerous that they couldn't comply," said Jimmy Hill, fire marshal for the city of L.A.'s Bureau of Fire Prevention and Public Safety, which came up with guidelines for alleviation.

Owners of the largest building in the district, St. Vincent Jewelry Center on Broadway, have been doing renovations over the past year that include upgrading sewer lines and air filtering systems. The building houses hundreds of wholesalers and several manufacturers who have managed to stay open through the renovations.

United Jewelry Mart on Broadway borrowed $12 million in March for planned refurbishment, according to its lender, Ed Ptacek, regional director of mortgage lender AMI Capital. He declined to say whether the United Jewelry Mart improvements are in response to environmental regulations, and building officials declined to comment.

Keeping jewelry manufacturing is a key goal of building owners. They are the economic engine of the area, and the stores that sell their wares need to be close to them.

"The jewelry sellers can go right upstairs and get the products and bring them down, If the manufacturers leave, this area would be dead," said Karabet Akpulat, a part owner of the St. Vincent Jewelry Center and owner of Nova Gold Imports Inc., a store on the first floor.

The area has thrived as an economic and ethnic melting pot for decades. Mexican craftsmen, Armenian jewelers fleeing civil war in Lebanon and Russians emigrating after the breakup of the Soviet Union all have congregated there -- along with wholesalers from Asia. and Israeli diamond dealers.