Endocrine Nervous System and Cardiovascular

Toxins are poisonous substances that can cause harm to human beings via one or more of its physiological systems. For example, DDT is a toxin used to kill insects but which also affects the human endocrine system. Tetrodotoxin is a toxin found in the venom of animals like frogs and pufferfish, but if it enters the human nervous system can cause paralysis or death. Mercury is a naturally-occurring element like tetrodotoxin, but exposure to the cardiovascular system in human beings can cause hypertension and even worse health effects. Although each of these toxins operates differently in the body, their consequences can be grave.

Whereas DDT is a synthetic chemical compound first developed in the late 19th century, both tetrodotoxin and mercury are naturally-occurring substances. Tetrodotoxin is manufactured in the bodies of venomous animals like pufferfish and certain types of poisonous frogs and stored in their livers or sex organs. Mercury, on the other hand, is a chemical element that is usually found in metals like cinnabar. Whereas Mercury has a silvery liquid appearance, tetrodotoxin is a "colorless crystalline solid," (NIOSH, n.d.). Of these three substances, only DDT has used as a pesticide. Until relatively recently, DDT was used heavily in the agriculture industry as a pesticide (NPIC, 1999). Because of its toxicity in human beings, DDT has been banned in the United States and some other countries. Mercury's toxic effects themselves are not used in the way that DDT is, but the element is used widely in the manufacture of thermometers, barometers, and other instruments, as well as compact fluorescent bulbs and some types of clocks (Blaszczak-Boxe, 2014). However, mercury has been used for thousands of years in various medical systems and was even used until the 20th century to treat syphilis (Blaszczak-Boxe, 2014). Unlike either DDT or tetrodotoxin, mercury is actually a metal, and is the only liquid metal in the periodic table. Mercury is also the only actual element (its symbol is Hg) of these three.

The characteristics of these toxins differ, which is why each acts differently on the human body. The endocrine system is vulnerable to DDT because DDT interferes with the "production, release, transport, metabolism, or elimination" of hormones (NIH, 2015). One of the ways DDT interferes with hormones in the human body is by mimicking hormones already in the body; another way is by binding to cells and blocking hormones, and also by blocking receptors (NIH, 2015). Its impact on hormones via the endocrine system is why DDT causes rats to become infertile, which is one of the many reasons why the toxin has been banned from use in agriculture (NPIC, 1999). Tetrodoxin enters the nervous system directly after it is ingested or via the skin, as it breaks the blood-brain barrier. When it enters the body, tetrodoxin blocks neuronal pathways, causing paralysis. The paralysis may be paralysis of the lungs, which causes the person to stop breathing and therefore to die (Bancroft, n.d.). Mercury can enter the body in a number of different ways, and is toxic not only to the cardiovascular system but to the nervous system and renal system as well. The cardiovascular system is vulnerable to the substance often because of its initial interference with the nervous system, as it can lead to the blockage of nerves that lead to escalations in heart rate. Yet unlike tetrodotoxin, the effects of mercury often take years to manifest; with tetrodoxin the time of action is extremely rapid.