Several children between the ages of 3 and 6 years have been admitted to a local hospital because of the encephalopathic crisis. They have lived in the same community all their lives. All have previously exhibited retarded psychomotor development. On physical examination, the children have diffuse abdominal pain and are experiencing nausea and vomiting. Head CT scans show marked cerebral edema. Laboratory studies show microcytic anemia. An investigator sent to the housing project where the children live finds a rundown apartment complex with extensive water damage, poor plumbing, and ventilation. Toxic exposure to which of the following substances best accounts for these findings?

Old flaking paint that is lead-based has a sweet taste, attracting small children to ingest it. The major risk to children from lead ingestion is neurologic damage. Venous blood lead levels should normally be less than 10 mg/dL. Ethylene glycol is found in antifreeze and can produce acute renal tubular necrosis. Kerosene, a hydrocarbon used in some household heating devices, can generate carbon monoxide fumes if not properly ventilated and can cause gastrointestinal and respiratory toxicity when ingested. Methanol ingestion can cause acute central nervous system depression, acidosis, and blindness. Household bleach (sodium hypochlorite) is a local irritant and is not likely to be found in the living conditions of these children.