Known Human Carcinogens and the Importance of Toxicology in Cancer Research

Aim of this article is to review the literature about known human carcinogens and emphasize the importance of toxicology in cancer research. Cancer etiology is multifactorial with toxins playing an important role, what accentuates the importance of multidisciplinary approach to cancer research, with toxicology playing a key role.


INTRODUCTION
The predominant view of cancer etiology is that the root cause lies at the genomic Koshiol and coworkers showed in the study that exposure to AFB1 is associated with gallbladder cancer 7 .
In 2013, a study was conducted to assess if aflatoxins contamination of wheat flour could be related to high-risk esophageal cancer in the Golestan region of Iran.
Authors demonstrated that in samples collected in esophageal cancer high-risk areas there were higher levels of AFB1 compared to low-risk areas of the same region 8 .
AFB1 exposure was associated also with gastric cancer development. A casecontrol study evidenced that AFB1 intake 3 was higher in gastric cancer patients than in controls, and that genetic polymorphism of CYP1A2 (rs2470890), one of the enzymes that metabolize AFB1, showed a lower risk of gastric carcinogenesis 9 .

ALCOHOL
Moderate alcohol drinking is defined as up to one drink per day for women and up to two drinks per day for men. Heavy alcohol drinking is defined as having 4 or more drinks on any day or 8 or more drinks per week for women and 5 or more drinks on any day or 15 or more drinks per week for men. Binge drinking is defined as consuming 4 or more drinks for women and 5 or more drinks for men in one sitting, typically in about 2 hours 10 11,12 ).
Moderate to heavy alcohol consumption is associated with 1.2-to 1.5-fold increased risks of cancers of the colon and rectum compared with no alcohol consumption 11,12,15 . Alcohol consumption has also been associated with deceased risks of kidney cancers and non-Hodgkin lymphoma in multiple studies 10 .

4-AMINOBIPHENYL
Historically, occupational exposure to 4aminobiphenyl mainly occurred during its production and its use as a rubber An increased risk of lung cancer has been observed in workers exposed to beryllium or beryllium compounds 27 .

HEPATITIS B VIRUS
In contrast to a majority of cancer types, the initiation of hepatocellular carcinoma   Melphalan is also used for regional arterial

MINERAL OILS
The name mineral oil has been used to describe many colorless, odorless liquids.
Most often, the term refers to a liquid by- 2) Skin cancer incidence rates increase from north to south, as do annual influence rates of UV radiation, while there seems to be a slight improvement in prognosis from north to south.

VINYL CHLORIDE
Vinyl chloride is a colorless gas that burns easily. It does not occur naturally and must be produced industrially for its commercial uses. Vinyl chloride is used primarily to make polyvinyl chloride (PVC) that is used to make a variety of plastic products, including pipes, wire and cable coatings, and packaging materials. Vinyl chloride is also produced as a combustion product in tobacco smoke. Workers at facilities where vinyl chloride is produced or used may be exposed primarily through inhalation. The general population may be exposed by inhaling contaminated air or tobacco smoke. In the environment, the highest levels of vinyl chloride are found in air around factories that produce vinyl products. If a water supply is contaminated, vinyl chloride can enter household air when the water is used for showering, cooking, or laundry. Vinyl chloride exposure is associated with an increased risk of hepatic angiosarcoma, as well as brain and lung cancers, lymphoma and leukemia 75 .

WOOD DUST
Wood dust is created when machines or tools are used to cut or shape wood. High amounts of wood dust are produced in sawmills, and in the furniture-making, cabinet-making, and carpentry industries.
Individuals who use machinery or tools to cut or shape wood are exposed to wood dust. When the dust is inhaled, it is