The correct option, "1 and 3 only," is accurate as it highlights significant sources of lead exposure that remain after the ban on leaded petrol. Smelting units can release lead particles into the environment, posing risks to workers and surrounding communities. Additionally, lead-based paints, commonly used in older structures, can degrade and produce lead dust or chips, particularly hazardous for children who may ingest them during normal activities. In contrast, pens and pencils typically do not contain lead, and while some hair oils and cosmetics may have heavy metal contamination, they are less prominent sources of lead poisoning compared to industrial and paint-related sources.