Radiation Protection and Environment

: 2018  |  Volume : 41  |  Issue : 2  |  Page : 104--105

International agency for research on cancer classification of carcinogens

 Ex RSSD BARC, Mumbai, Maharashtra, India

Correspondence Address:
Dr. Pushparaja
Ex RSSD BARC, Mumbai, Maharashtra

How to cite this article:
Pushparaja. International agency for research on cancer classification of carcinogens.Radiat Prot Environ 2018;41:104-105

How to cite this URL:
Pushparaja. International agency for research on cancer classification of carcinogens. Radiat Prot Environ [serial online] 2018 [cited 2022 May 18 ];41:104-105
Available from: https://www.rpe.org.in/text.asp?2018/41/2/104/239686

Full Text

Daily we are exposed to so many chemical and physical agents which can initiate mutation in a cell. The mutated cell, in general, gets killed and eliminated from the body by the repair mechanism existing in the body itself. There are hundreds of agents that can cause this mutation, and hence, it is thus very difficult to say which exposures are associated with cancer of a specific organ or site.

However, this information is important for planning cancer control program and cancer treatment. This also is a critical input for the analysis of epidemiological studies and for planning of experimental investigation. Every cancer patient wonders what factor– environmental, occupational, dietary or consumer exposure contributed or caused the cancer. A lot of information, epidemiological, and experimental, on the above aspects are being published worldwide at the cost of billions of dollars.

An International organization called International Agency for Research on Cancer (IARC) continuously reviews the published data based on occupations, physical agents, biological agents, and over 100 chemicals. Based on the review, the agency classifies the agents as follows:

Carcinogenic to humans (Group 1)Probably carcinogenic to humans (Group 2A)Possibly carcinogenic to humans (Group 2B)Not classifiable (Group 3), andProbably not carcinogenic to humans (9 Group 4).

Now, for over 4 decades, the IARC, using international experts in the fields, critically reviews the data to evaluate the carcinogenicity of each agent to identify the cancer type, cancer site, and the nature of some association with the agent (IARC monographs 1–99). The IARC volumes provide up-to-date information on the subject. Subsequently, The IARC monographs, 6 volumes - 100 A to 100 F were published. Volume 100 D published in 2012, covers radiation.

The types of radiation covered in the volume include solar and ultraviolet radiation, X and gamma radiation, neutron radiation, internalized alpha emitters, and internalized beta emitters. The evaluations are done by international working group of scientists. Other factors associated with an increased cancer risk not covered in the IARC Monographs, they are as follows: genetic traits, reproductive status, and some nutritional factors are not included in this review.

The last volume on the evaluation of carcinogenic risk to humans, was published in 2018 is the monograph volume No. 114 on: “Red meat and Processed meat.”


For each agent that IARC classifies as carcinogenic to humans, the authors compiled lists of all the cancer sites which have “sufficient evidence” or “limited evidence” of an association in humans [Table 1].{Table 1}

For the purposes of this analysis, the authors collected the information from the IARC review volumes. Sufficient evidence in humans means that a causal relationship has been established, and that chance, bias, and confounding could be ruled out with reasonable confidence, whereas limited evidence in human means a causal relationship was credible, but that chance, bias, or confounding could not be ruled out with reasonable confidence. Based on the data and the data from the currently reviewed studies, the cancer sites were identified for each known or suspected carcinogen, the information is listed by the authors.[1]


This is a good review on the causes of cancers at specific sites. However, a lot more needs to be done to establish the carcinogenic potential of any agent at lower exposure conditions where there are no scientifically sound data. Epidemiology may not provide any information since the concentrations are very low. Finally, exposure-to-effect may not follow no-threshold model hypothesis at lower exposure levels.

It is also reported that there are no identified causes for some common human cancers. When cause and exact mechanism of the initiation and progression of the cancers are not known, prevention is not possible.

A part of the note to the readers given by the publishers is quoted here. “Inclusion of an agent in the monograph does not imply that it is a carcinogen. And an agent which has not yet been evaluated in a monograph does not mean it is not carcinogenic.” Through this note, probably, the Agency accepts all the possible uncertainties in the assessment and review. The assessments are qualitative in nature and no recommendations are made for regulation and legislation.

The last volume on evaluation of carcinogenic risk to humans was published in 2018 is the monograph volume No. 114 on: “Red meat and Processed meat.”

During the use, mobile phones and cordless phones emit radiofrequency (RF) radiation. Other sources of the radiation are mobile phone base stations, Wi-Fi access points, laptops and tablets. The exposures to RF radiation can be long-term or round-the-clock. Cancer risks of the RF radiation emitted by some devices in the frequency range from 30 kHz to 300 GHz was also evaluated by the IARC for any possible risk for head and brain tumors. It was found that it is Group 2B – a possible human carcinogen. The data are based on animal studies and epidemiological studies (Hardell, 2017).[2]


1Cogliano VJ, Baan R, Straif K, Grosse Y, Lauby-Secretan B, El Ghissassi F, et al. Preventable exposures associated with human cancers. J Natl Cancer Inst 2011;103:1827-39.
2Hardell L. World Health Organization, radiofrequency radiation and health – A hard nut to crack (Review). Int J Oncol 2017;51:405-13.