Toxicology Literature Review

Toxicology Literature Review

Introduction

Cancer is a complex class of diseases that are a major cause of alarm to the human population today. Its study dates back to the sixteenth century when Giovanni Morgagni applied autopsies to relate patients’ illnesses to the pathological findings in dead bodies laying a good foundation for oncology. In all types of cancers, the affected cells divide continuously spreading and damaging the surrounding tissues. Researchers have associated cancers with certain hereditary and non-hereditary factors. However, experts in the field still believe that most cancers are sporadic and of unknown etiology. Nevertheless, it is still important to learn and take precautions of the known mutagens and carcinogens to reduce the risk of having cancer.

Carcinogens are agents or substances that are capable of causing cancer in living body cells. They cause alteration of genes changing how normal cells function and especially the manner in which they grow and divide. However, carcinogens do not always cause cancer. For a carcinogen to be cancerous, it depends on other factors such as the type and period of exposure to the agents or substances, or a person’s susceptibility to the carcinogens depending on their genetic make-up. On the other hand, mutagens are substances or agents that induce hereditable changes to the structure of deoxyribonucleic acid (DNA) in certain body cells. As such, carcinogens can be mutagens and mutagens can be carcinogens. However, although most carcinogens are mutagens, not all of them are. The ability of a substance or an agent to induce cancer or mutation in an organism’s body is thus strongly correlated (De Serres and Hollaender, 2012).

Various associations of experts have come up with different classifications of carcinogens. As aforementioned, although a majority of the carcinogens are mutagenic, there are some which are non-mutagenic. There has been established a positive correlation between short-term carcinogenic assays and carcinogenicity for substances and agents that are both mutagenic and carcinogenic (McCoy, Rosenkranz, & Klopman, 2013). However, in some carcinogens, mutagenesis assays do not yield evidence of positive results in the short-term tests. Examples of these carcinogens are alcohol and estrogen. These carcinogens stimulate the rate of mitosis in the affected cells reducing the likelihood of repair of damaged DNA during DNA replication.

Carcinogens and the Cancer they Cause

Different carcinogens have distinct effects on human beings. Albeit some carcinogens may put one at a risk of contracting cancer in a short period of exposure, some take a lot of years of constant exposure to put one at a risk of cancer such as alcohol. Exposure of certain cancerous agents and substances at the workplace generally puts people at a higher risk of getting cancer since it happens on an almost every work day. Some of the common carcinogens in the world today include tobacco, asbestos and arsenic.

Tobacco is a plant that is proven to contain various carcinogenic properties. According to (Vrana, Kernand Anderson, 2017), tobacco contains more than sixty carcinogenic compounds. Smoking or inhalation of tobacco is associated with many cancers such as those of the lungs, larynx, oesophagus, kidney, cervix, bladder, oral cavity and the stomach. Carcinogens in tobacco have to be metabolically activated to form DNA adducts. When cellular repair systems fail to remove the DNA abducts, miscoding occurs during DNA replications. The abductions may persist leading to somatic mutation increasing the probability of developing cancer. Asbestos is a carcinogen that is closely associated with lung cancer, larynx cancer and mesothelioma. They are naturally occurring minerals that are highly used in industries. Effects of asbestos depend on the fibre inhaled and its composition. Asbestos as a carcinogen can act independently or with other carcinogens and especially tobacco. Elimination of asbestos fibre longer than 5 um become impossible for phagocytes in the body leading to cell abnormalities such as inflammation, fibrosis or carcinogenesis (Hubaux, Lam, Martinez, & Enfield, 2012). When reactive oxygen and nitrogen acts upon a fibre that has not been successfully eliminated through phagocytosis, the cell’s DNA