**2. Effects of cadmium on some physiological parameters in human**

Cadmium chloride is a colorless heavy metal that can dissolve in ethanol, methanol, and water. It is considered a major environmental pollutant as a result of its widespread industrial use. It is present not only in soil and food, but also in water and air. So, it could be contaminated through food intake and could be released into water as a by-product. Combustion of coal and oil could also expose individuals to it [6]. It has a long half-life of between 15 and 30 years in humans due to its low rate of excretion from the body [7, 8].

International Agency for Research on Cancer (IARC) has identified cadmium as a known or probable human carcinogen. It has also been listed in the International Register of Potentially Toxic Chemicals (IRPTC) of the United Nations Environment Program (IRPTC), even as the World Health Organization (WHO) estimated 500 micrograms per week cadmium as the safe level for human ingestion [9].

Fish, liver, grains, and vegetables remain major sources of dietary cadmium [10].

Cadmium chloride has various lines of applications and is mostly used industrially. The major industrial applications of cadmium include the production of alloys, pigments, and batteries [11].

Invariably, people are exposed to cadmium on a daily basis, with common exposure in industrial work places, plants, soils, and from smoking. Due to its low permissible exposure to humans, over exposure may occur even in situations where trace quantities of cadmium are found [12]. Shortness of breath, pneumonitis, and pulmonary edema can all be signs of more serious respiratory system injuries [13, 14].

Long-term accumulation of cadmium in a number of tissues, including the kidneys, liver, CNS, and peripheral neuronal systems, may have hazardous effects at the peripheral level. It could cross the blood-brain barrier at the CNS and enter the CNS through the nasal mucosa or olfactory pathways. Exposure to cadmium is implicated

*Ameliorative Effects of Zinc and Vitamin E on Physiological Changes after Exposure to Heavy… DOI: http://dx.doi.org/10.5772/intechopen.111518*

in hyperactivity, increased aggression, impaired social memory processes, and altered drinking behavior [15, 16].

### **2.1 Mechanism of action**

Cadmium acts as catalysts for biochemical reactions, regulators of gene expression, second messengers in signaling pathways, and co-factors for vital enzymes notorious for regulating physiological, pathological, and behavioral functions [7, 17]*.*

In comparison with other brain regions, the hippocampus collects the divalent metals to a larger amount. The hippocampus impairment that results from heavy metal exposure has been linked to behavioral changes. Animal studies using Cd exposure also show behavioral changes in this approach. Reduced memory and altered anxiety and fear responses have been seen in rats exposed to Cd [18]*.*

### **2.2 Zinc and Vitamin E**

### *2.2.1 Zinc*

Zinc (Zn), a trace element necessary for live cells and an important heavy metal for many enzymes, is involved in DNA replication, transcription, and protein synthesis, which all have an impact on cell division and differentiation [19]. It performs the task of attaching particular genes to tetrahedral bonds, causing transcription, and is thus directly implicated in the translation stage of DNA element gene expression.

Zinc deficiency may prevent the production of new proteins, which would reduce the amount of protein and cause a buildup of amino acids. This is due to zinc, a ribosome structural element that maintains the structural integrity of the ribosomes. In the absence of it, ribosomes break down [19].

By the antioxidant system's action, it stops cell damage. It performs many different roles and is a crucial part of the antioxidant defense system [20, 21].

### *2.2.2 Vitamin E*

The collection of eight fat-soluble compounds includes vitamin E. It can be discovered in many foods and oils. Alpha-tocopherol is mostly found in nuts, seeds, vegetable oils, fortified cereal, and green vegetables. Significant levels are also present in green leafy vegetables and fortified cereals. Food-based vitamin E is not known to be harmful. However, there is proof that extremely high doses of vitamin E supplementation might cause pro-oxidant damage [22, 23].

Vitamin E plays a role in the prevention of diseases like cancer, Alzheimer's disease, HIV/AIDS, and others by preventing oxidative stress, protecting cell membranes, controlling platelet aggregation, and activating protein kinase C. According to other theories, vitamin E regulates gene expression and cell signal transmission [24–26].

### *2.2.3 Anxiety*

Many conditions that produce trepidation, fear, concern, and worrying are together referred to as anxiety. It is described as a feeling that is accompanied by tense sensations, anxious thoughts, and physical changes like raised blood pressure. Fear is a reaction to an immediate threat, actual or perceived; anxiety is the anticipation of an impending threat [27, 28].

Muscle tension, agitation, exhaustion, and attention issues are frequently present in conjunction with it. Although experiencing anxiety occasionally is normal, a person may develop an anxiety disorder. Drug addiction, drug withdrawal, and genetic factors are all possible causes of anxiety disorders [27].

Therapy, medication, and lifestyle modifications are all potential treatment options. Worry, which is considered to be a result of metacognitive beliefs, is something that metacognitive treatment aims to eliminate [29].

This chapter addresses how cadmium chloride impacts the CNS to create anxiety as well as the role of zinc and vitamin E in reducing its effects on anxiety levels. Exposure to cadmium chloride may change the physiology of biological organs and systems.
