How are chemicals both harmful and helpful to humans ?

Chemicals can enter and irritate the nose, air passages and lungs. They can become deposited in the airways or be absorbed by the lungs into the bloodstream. The blood can then carry these substances to the rest of the body. Ingestion (swallowing) of food, drink or other substances is another route of exposure.

Explanation:

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answer; /// the amount of material dissolved in a measure of liquid(concentration) the above statement is (true); /// good luck