Statement 1 is Correct: Smelting units are a major source of lead poisoning as the process of extracting lead from ores releases lead particles into the air and surrounding soil. Statement 2 is Incorrect: Pencils do not contain the element lead; the "lead" used in pencils is actually a non-toxic mixture of graphite (a form of carbon) and clay. Statement 3 is Correct: Lead-based paints are a significant source of exposure, especially when the paint deteriorates into dust or chips, which can be easily inhaled or ingested. Statement 4 is Incorrect: While some specific traditional eye cosmetics (like surma) may contain lead, standard hair oils and modern commercial cosmetics are not classified as primary or common sources of lead poisoning.