Stimulating the immune system is not a common mechanism of toxicity. The other options are all common mechanisms by which toxic substances can exert their effects.

Biotransformation is the process by which a toxic substance is converted into a more toxic form. Metabolism is the general term for the chemical reactions that occur in the body, including biotransformation. Detoxification is the process by which a toxic substance is converted into a less toxic form. Excretion is the process by which a toxic substance is removed from the body.

Enzymes are not receptors. Ligand-gated ion channels, G protein-coupled receptors, and nuclear receptors are all types of receptors that can be targeted by toxic substances.

Carcinogenicity is the ability of a toxic substance to cause cancer. Mutagenicity is the ability of a toxic substance to cause mutations in DNA. Teratogenicity is the ability of a toxic substance to cause birth defects. Neurotoxicity is the ability of a toxic substance to cause damage to the nervous system.

Injection is not a common route of exposure to toxic substances. Inhalation, ingestion, and dermal contact are all common routes of exposure.

Toxicology is the study of the effects of toxic substances on living organisms. Pharmacology is the study of the effects of drugs on living organisms. Epidemiology is the study of the distribution and causes of disease in populations. Risk assessment is the process of evaluating the potential risks of a toxic substance to human health and the environment.

Vitamins are not toxic substances. Heavy metals, pesticides, and solvents are all common types of toxic substances.

The no observed adverse effect level (NOAEL) is the lowest dose of a toxic substance that can cause an adverse effect. The threshold limit value (TLV) is the maximum concentration of a toxic substance in air that is considered safe for workers to be exposed to over an 8-hour workday. The lowest observed adverse effect level (LOAEL) is the lowest dose of a toxic substance that has been shown to cause an adverse effect. The maximum tolerated dose (MTD) is the highest dose of a toxic substance that can be tolerated without causing severe adverse effects.

Improved health is not a common type of adverse effect caused by toxic substances. Cancer, birth defects, and neurological damage are all common types of adverse effects caused by toxic substances.

Excretion is the process by which a toxic substance is removed from the body. Metabolism is the general term for the chemical reactions that occur in the body, including biotransformation and detoxification. Biotransformation is the process by which a toxic substance is converted into a more toxic form. Detoxification is the process by which a toxic substance is converted into a less toxic form.

Medical exposure is not a common type of toxic substance exposure. Occupational exposure, environmental exposure, and recreational exposure are all common types of toxic substance exposure.

Ecotoxicology is the study of the effects of toxic substances on the environment. Toxicology is the study of the effects of toxic substances on living organisms. Pharmacology is the study of the effects of drugs on living organisms. Epidemiology is the study of the distribution and causes of disease in populations.

Food contamination is not a common type of environmental exposure to toxic substances. Air pollution, water pollution, and soil pollution are all common types of environmental exposure to toxic substances.

Distribution is the process by which a toxic substance is distributed throughout the body. Absorption is the process by which a toxic substance enters the body. Metabolism is the general term for the chemical reactions that occur in the body, including biotransformation and detoxification. Excretion is the process by which a toxic substance is removed from the body.

Gardening is not a common type of recreational exposure to toxic substances. Smoking, alcohol consumption, and drug use are all common types of recreational exposure to toxic substances.