Other exposures

Other exposures account for 5% or less of the cancer burden. Occupational exposures have been linked with lung, bladder, and haematopoietic malignancies. Breast cancer has consistently been associated with early age at menarche, late age at first birth, and late age at menopause with relative risks of the order of 2.0 or less. Parity is associated inversely with endometrial and ovarian cancer.

Although most types of cancer are more common in urban than in rural areas, few causal links with environmental pollutants have been firmly established. It has been estimated that 1% of lung cancer deaths in the US are attributable to air pollution. While exposure to ionizing radiation at doses of 500-2000 mSv is known to be carcinogenic, exposures of this magnitude are unusual—about 1% of the deaths of the Japanese atomic bomb survivors could be attributed to radiation. The average per capita dose from all sources of ionizing radiation is about 3.4 mSv per year, of which about 88% is from natural sources and the remainder primarily from medical exposures. Extrapolation from data on people exposed to doses of 500 mSv or more suggests that 1-3% of all cancers might be attributable to radiation arising largely from natural sources. No clear association with exposure to extremely low frequency magnetic fields has been established.

Table 2.1 Estimates of the proportion of cancer attributable to specific exposures

Exposure

Estimates (%)

USA

USA

Nordic countries

Worldwide

Best estimate

Range

Men

Women

Tobacco

30

(25-40)

30

19

9

15

Passive smoking

<1

<1

Alcohol consumption

3

(2-4)

3

2

2

Diet

35

(10-70)

30

?

?

Obesity

<1

(-5a-2)

<1

1

30-40

Food additives

1

Sedentary lifestyle

5

Infections

10

(1-?)

5

2b

3b

16

Sexual behaviour

1

(1)

Occupation

4

(2-8)

5

3

<1

Perinatal factors/growth

5

Reproductive factors

6

(0-12)

3

Environmental pollution

2

(1-5)

2

Industrial products

<1

(<1-2)

Man-made ionizing radiation

2

2

Random

2

<1

<1

Solar and ultraviolet radiation

4

5

Medicines and procedures

1

(0.5-3)

1

Socio-economic status

3

Geographical factors

3

(2-4)

5

Family history of cancer

1

a Allows for protective effect of preservatives b Infection with human papillomavirus or Helicobacter pylori ? No precise data available a Allows for protective effect of preservatives b Infection with human papillomavirus or Helicobacter pylori ? No precise data available

Some pharmaceutical agents (e.g. immunosuppressive agents, anti-neoplastic drugs, and hormonal preparations) are human carcinogens.

1 Doll, R. and Peto, R. (1981) The causes of cancer: quantitative estimates of avoidable risks of cancer in the United States today. Journal of the National Cancer Institute 66,1191-308.

2 Parkin, D.M., Pisani,P.,Lopez,A.D.,and Masuyer, E. (1994) At least one in seven cases of cancer is caused by smoking. Global estimates for 1985. International Journal of Cancer 59, 494-504.

3 Blot,W.J., Li, J.Y., Taylor, P.R., Guo,W.,Dawsey, S.,Wang, G.Q., et al (1993) Nutrition intervention trials in Linxian, China: supplementation with specific vitamin/mineral combinations, cancer incidence, and disease-specific mortality in the general population. Journal ofthe National Cancer Institute 85,1483-92.

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