Final answer:
Toxicants that harm the immune system include allergens. Endocrine disruptors like dioxins and PCBs can also affect the immune system by interfering with the endocrine system, even at low exposure levels.
Step-by-step explanation:
Toxicants that cause harm by affecting the immune system include allergens. Allergens are substances that can lead to an immune response in certain people, resulting in allergic reactions that can range from mild to severe. Other substances such as antibiotics are not designed to harm the immune system but to fight off bacterial infections. Teratogens are agents that can cause birth defects during embryonic development. Hormones are chemical messengers in the body, and while they can be affected by toxicants, they are not toxicants themselves. Neurotoxins are substances that are toxic to the nervous system, not primarily the immune system.
In the context of environmental biology, it is vital to be aware of endocrine disruptors, which are chemicals that can interfere with the body's endocrine system. These include substances such as dioxins, polychlorinated biphenyls (PCBs), and plasticizers like bisphenol A (BPA). Endocrine disruptors can have profound effects on development, reproduction, the nervous system, and the immune system, and they may cause endocrine disruption even at low levels of exposure.
Overall, an understanding of how various toxicants affect different systems within the body is essential in the field of environmental toxicology. This branch of biology looks at the adverse effects of chemical, biological, and physical agents on living organisms in the ecosystem, including humans.