Carcinogenic contaminants such as nitrates, pesticides, certain metals and metalloids, etc,.

A few major environmental carcinogens causing cancer include 

outdoor air pollution, 
indoor air pollution due environmental tobacco smoke, 
food contamination by food additives, 
carcinogenic contaminants such as nitrates, pesticides, certain metals and metalloids, etc,.

TABLE 3 DISTRICT-WISE AGE-STANDARDIZED INCIDENCE RATES

District	N	ASIR (PER 1000000) All ages	0 to 14	15 to 24	25  to 49	50 to 74	75+
Coimbatore(M)	2560	12.5	0.34	0.30	2.26	7.88	1.73
Coimbatore(F)	3375	15.4	0.46	0.28	4.73	9.03	0.99
Erode(M)	1246	9.25	0.20	0.21	1.76	6.12	0.97
Erode(F)	1567	10.99	0.14	0.21	3.82	6.21	0.60
Tiruppur(M)	1234	8.29	0.34	0.23	1.47	5.49	0.76
Tiruppur(F)	1633	10.42	0.17	0.26	3.58	5.90	0.51
Salem(M)	435	2.03	0.08	0.07	0.44	1.25	0.20
Salem(F)	699	3.20	0.01	0.02	1.26	1.79	0.12
Namakkal(M)	402	3.88	0.16	0.09	0.78	2.40	0.45
Namakkal(F)	602	5.50	0.13	0.11	2.04	3.03	0.19
Nilgiris(M)	256	5.87	0.18	0.22	1.15	4.06	0.26
Nilgiris(F)	386	8.06	0.18	0.13	3.13	4.18	0.44

TABLE 2 PROMINENT CANCER TYPES AMONG MEN AND WOMEN FOR ALL DISTRICTS

Prominent cancers among men	Coimbatore	Erode	Tiruppur	Salem	Namakkal	Nilgiris
Head and Neck	848	457	420	102	133	83
Gastrointestinal	487	265	258	77	91	50
Genitourinary	237	108	121	30	43	17
Respiratory	248	94	86	32	26	22
Blood	288	116	112	55	38	40
Prominent cancers among women	Coimbatore	Erode	Tiruppur	Salem	Namakkal	Nilgiris
Gynaecological	1007	536	534	183	219	111
Breast	1103	455	487	144	173	135
Gastrointestinal	300	158	169	39	46	31
Head and Neck	297	130	136	33	48	25
Respiratory	95	18	37	9	9	11
Genitourinary	47	26	25	33	7	5
Blood	180	79	81	33	16	19

A recent study in Taiwan has found that other than cigarette smoking and betel quid chewing, heavy metals such as arsenic and nickel in farm soils may be risk factors for oral cancers [15]. High concentrations of heavy metals such as Chromium, Arsenic and Lead have been found in the industrial and residential areas of Coimbatore district [16]. Investigations relating to associations of heavy metals and specific cancer types could be done in future to assess the carcinogenic effects of the soils of the present study area. Certain infectious agents have proved to show strong association with specific cancer types. Helicobacter pylori, hepatitis B and C viruses, and human papilloma viruses (HPV) were responsible for 1.9 million cases, mainly gastric, liver, and cervix uteri cancers in a global cancer study [17].

Conclusion

Although elucidating biological pathways is important, an association between environmental contaminants and cancers needs to be well established in a terms of medical sciences. Such medical examinations and correlated results will provide an important contribution to the debate on reducing the exposures to air, soil and water pollution. The main limitation of our study is the lack of information to individual risk factors for cancers such as smoking and alcohol consumption. It is reported that the individual risk factors are correlated with the ambient air pollution levels. Another limitation is the use of environmental monitoring data, which do not necessarily represent individual exposures. Although measurements of pollutants at certain selected locations may be used, they can result in misclassification of exposure because individuals may behave differently from the general population. Therefore our study is a preliminary attempt to assess the age based response to environmental carcinogens. We have observed that a multi-disciplinary approach is required to investigate the risk factors associated with cancer along with the traditional practices. Through this we have provided a directive so as to target treatment and preventive and awareness measures in terms of exposures, lifestyles and behavior aspects.  

http://www.iapsmupuk.org/journal/index.php/IJCH/article/view/645/html_39