PONCA CITY, Okla. (May 2)—The Paper, Allied-Industrial, Chemical and Energy Workers International Union has issued a warning letter regarding potential quality problems with tires made with carbon black produced at Continental Carbon Inc.'s Ponca City plant. The letter—sent April 30 to the Rubber Manufacturers Association—was issued in conjunction with National Tire Safety Week, observed April 29-May 3, the union said. The correspondence highlighted the replacement of experienced workers with less experienced ones in Ponca City as potentially leading to "the production of substandard carbon black that could create cracks in tires." About 85 members of PACE Local 5-857 were locked out May 7, 2001, after the union failed to ratify Continental Carbon's final economic proposal. To commemorate the one-year anniversary of the lockout date, union members are holding a picnic, march and rally on May 11.