Physical and Health Hazards Understanding the difference between toxicity and hazard is important. Toxicity is the inherent ability of a substance to cause adverse health effects. Hazard refers to the likelihood that adverse health effects might occur. Exposure links toxicity and hazard. Without exposure, a toxic chemical cannot cause adverse health effects.
Exposure can occur in three general ways, ingestion, skin contact and inhalation.
Ingestion can occur by mouth pipetting, which is why this technique is banned. Thus no food or drink is allowed in laboratories, and hand washing is critically important. Ingestion of small doses of toxic substances over time can cause systemic diseases, such as central nervous system disorders, kidney and livery dysfunction, and cancer. Skin contact includes absorption through the skin and reaction on the skin surface causing dermatitis. Cuts, abrasions, dermatitis provide an easier route for absorption than intact skin.