RIO DE JANEIRO, Brazil – Concerned U.S. consumers can choose not to buy some Brazilian products that might be tainted by slavery, such as tropical hardwoods. For products that few people buy directly, such as soybeans or pig iron, the best way to express an opinion is to write to the heads of U.S. companies that do buy them.

Among many active U.S. importers are:

• Nucor Corp., 2100 Rexford Rd. Charlotte, NC 28211; Daniel R. DiMicco, president and CEO (pig iron).

• Cargill Inc., P.O. Box 9300, Minneapolis, MN 55440; Warren R. Staley, chairman and chief executive officer (soybeans).

• ConAgra Foods Inc., One ConAgra Drive, Omaha, NE 68102; Bruce C. Rohde, chairman, CEO and president (processed beef).

• BR-111, 9590 Lynn Buff Court, Laurel, MD 20723; Ricardo Moraes, owner (rainforest hardwoods).

• DLH Nordisk Inc., 2307 W. Cone Blvd. 200, Greensboro, NC 27408; Stewart Sexton, president (rainforest hardwoods).

In the case of Brazilian hardwoods, only wood certified by the international Forest Stewardship Council (www.fsc.org) can be presumed to be free from the slavery taint and to come from sustainable forestry. The council’s approval, indicated by a check mark whose long end extends to form a tree, will be on a label accompanying the wood. Expect this wood to cost about 10 to 30 percent more than uncertified equivalents.

The oldest and largest U.S. supplier of FSC-certified hardwood is EcoTimber in San Rafael, Calif. Conscious Flooring of Holbrook, Mass., sells EcoTimber’s wood on the East Coast.

More generally, opponents of Brazilian slavery can write Brazil’s ambassador in Washington, Roberto Abdenur, to express their support for Brazil’s efforts to stop it. His address is Brazilian Embassy, 3006 Massachusetts Ave. N.W., Washington, DC 20008.

Sen. Tom Harkin, D-Iowa, is Congress’ leader when it comes to global working conditions. His address is 731 HSOB, Washington, DC 20510.

The American Anti-Slavery Group offers material on enslaved charcoal workers in Brazil. Go to www.iabolish.com/index.htm, click on “Slavery Today,” then on the map of South America, then on Brazil.

London-based Anti-Slavery International (www.antislavery.org) reports regularly on slavery in Brazil. Write “Brazil” in the home page’s search box.

Other groups concerned about modern slavery in rural Brazil include:

• The U.N. International Labour Organization (www.ilo.org).

• The International Labor Rights Fund (www.laborrights.org).

Groups that are trying to halt Amazon deforestation and related ills such as slavery include:

• Greenpeace International (www.greenpeace.org) Go to the “Campaigns” link, then click on “Protect Ancient Forests,” then on “Amazon.”

• Environmental Defense (www.environmentaldefense.org). Go to “Our Programs” and click on “Learn More,” then on “International.”

• Rainforest Relief (www.rainforestrelief.org).

•World Wildlife Fund-Brazil (www.wwf.org.br).