Lead can enter the body primarily through which pathways?

Lead primarily enters the body through the digestive and respiratory systems, which is why this choice accurately reflects the main pathways of lead exposure.

When lead-contaminated dust or particles are inhaled, they can enter the respiratory system and subsequently be absorbed into the bloodstream. Similarly, ingestion of lead through contaminated food, water, or surfaces leads to absorption through the digestive system. This route is particularly significant in children, who may inadvertently ingest lead through hand-to-mouth behaviors after playing in lead-contaminated environments.

While the other pathways listed may involve potential exposure to lead, they are not the primary means of entry. Skin absorption can occur in rare cases and is generally less efficient for lead compared to inhalation or ingestion. Direct injection is not a common or natural pathway for exposure to lead in everyday situations. Osmosis, in this context, does not apply as a pertinent method for lead entry into the body. Therefore, focusing on the established pathways of ingestion and inhalation provides a clear understanding of how lead enters the human body.