Editorialist: There would seem to be little hazard for consumers associated with chemicals used in treated lumber because the lumber is used outside where fumes cannot accumulate. However, immediate steps should be taken to determine the safety of these chemicals since consumers could ingest them. If the lumber is used for children' s playground equipment, youngsters could put their mouths on the wood, and if it is used to contain soil in a vegetable garden, the chemicals could leach into the soil. Which one of the following most accurately expresses the main conclusion of the editorialist's argument? ['The chemicals used in treated lumber are apparently not dangerous to the consumer.', 'Treated lumber is more dangerous than was once believed.', 'Parents should not allow children to put their mouths on playground equipment.', 'The effects on humans from the chemicals in treated lumber should be studied.']