Background
Methods
Developing radiation risk scenarios
Risks from air pollution
Risks from obesity
Risks from smoking and passive smoking
Results and discussion
Exposure and risk scenarios
Exposure scenario | Exposure | Mortality risk+
| Notes |
---|---|---|---|
Examples of radiation exposures not due to Chernobyl
| |||
General population (background exposures)
| |||
UK average (natural + medical) | 200 mSv |
1 %
| Lifetime (~75 yr) exposure to 2.7 mSv yr-1 UK average annual dose. |
Exposure at UK limit for radon exposures in the home [49] | 750 mSv |
3.7 %
| Lifetime (~75 yr) exposure to UK limit 200 Bq m-3 radon gas ≈ 10 mSv yr-1 dose. Above this limit, action must be taken to reduce radon in houses in the UK. Dose depends on time spent at home and doses at this high rate are rare. |
Working population (above background)* | |||
UK average for classified radiation workers [50] | 18 mSv |
0.07%
| Average current dose (above background) of classified workers in the nuclear industry of 0.6 mSv yr-1 accumulated over a 30 year working period. |
Long haul air crew [51] | 135 mSv |
0.54%
| Typical exposures in the range 3–6 mSv yr-1: assume 4.5 mSv yr-1 over 30 yrs |
Exposures after Chernobyl (above background)* | |||
General population
| |||
Residents of "strict control zones" (areas > 555 kBq m-2 137Cs). | 50 mSv |
0.25%
| Accumulated dose for approximately 10 year period after the accident [37, 52] |
Annual dose limit to populations of the Chernobyl affected areas, 1990's | 75 mSv |
0.37%
| If external + internal dose exceeded this limit, measures had to be taken to reduce dose. Accumulated dose at 1 mSv yr-1 over 75 yr lifetime [53] |
Consumer of sheep meat from the most contaminated areas in the UK | 4.1 mSv |
0.02%
| Consumption (at a high rate) of lamb from farms most affected by Chernobyl for 75 year period (assumed mean 137Cs = 500 Bq kg-1 in 1986, declining with effective half life 25 yr). Over-estimate of likely real exposures. |
Working population
| |||
Unofficial residents of the 30-km exclusion zone. In late 1990's range of doses in a number of villages [2], Ukrainian sector 30 km zone was 1–6 mSv y-1
| 255 mSv |
1.0%
| Illustrative of higher exposures: person of working age (25) who received 100 mSv during period to 1995, then returned to Zone in 1996 and received 6 mSv yr-1 in 1996 declining (with effective half life 25 years) to age 75 in 2036. N.B. some (uninhabited) areas of the Zone would give much higher doses. |
Chernobyl emergency workers [37]: Average High dose group | 100 mSv 250 mSv |
0.4%
1.0%
| Accumulated risk from exposures during 1986–87. Does not include very high exposures to those who suffered from ARS. Working population. |
Exposure scenario | Exposure | Health endpoint | Approximate lifetime increased mortality |
---|---|---|---|
Living in Central London compared to Inverness. | Mix of air pollutants indicated by average PM2.5 = 6.9 μg m-3 higher. | Mortality |
2.8 %
Postulated 2.8% higher air pollution related mortality in central London compared to Inverness (see text). |
N.B. Extrapolates from data in the US. May be confounding factors which, if accounted for, would change the excess risk. Time-lag between exposure and effect is uncertain. | |||
Passive smoking – risk to non-smoker at home if spouse smokes. | Mix of pollutants in secondhand smoke. | Mortality |
1.7 %
1.7% lifetime excess IHD mortality risk from passive smoking: average for men and women [36]. |
N.B. Heart disease risk: does not include strokes or the (significantly lower) risk from lung cancer or other illnesses. May be confounding factors/limitations of meta-analysis data. | |||
Chernobyl emergency workers in the 30-km Zone 1986–87. | Radiation exposure: 100 mSv 250 mSv Illustrative of mean (100 mSv) and high (250 mSv) doses: 4% of workers received doses >250 mSv. | Mortality |
0.4 %
1.0 %
Predicted 4% risk of fatal cancer for 1000 mSv dose to working age population. |
N.B. Uncertainty in extrapolation from high dose and dose rate Japanese data to these chronic low doses. If the DDREF was not applied, mortality risk would increase by a factor of 2. Time lag between exposure and effect is generally long (> 10 years) for solid cancers, but is shorter (< 15 years) for leukaemia. Note that 134 ARS victims received much higher doses than 250 mSv. |
Risk scenario | Average Years of Life Lost (YOLL) | Notes |
---|---|---|
Smoking
Male doctor who is a lifetime smoker compared to non-smoker. | 10 | Ref. [6]. Average smoking habit: 18 a day from age 18. |
Obesity
White male aged 35 who is obese (BMI = 30.0–39.9) or severely obese (BMI >40): risk relative to BMI = 24. | Obese: 1–4 a
Severely obese: 4–10a
| Ref. [26]. There is controversy over the BMI-mortality relationship (see text). However, increased mortality at BMI > 30 has been observed in a number of studies, though there is uncertainty in excess mortality rate and hence YOLL. |
Radiation
Atomic bomb survivor who was in the most exposed group: within 1500 metres of the hypocentre. Shielded whole body kerma > 1 Gy, mean 2.25 Gy. | 2.6 (1.3–5.2)a
| Ref. [19]. Only represents YOLL of bomb survivors. Few people close to the hypocentre survived the combination of blast effects, burns and ARS. |
Radiation risks
Air pollution risks – time series vs. cohort studies
Uncertainties
Risk factor | Uncertainty |
---|---|
Air pollution: 10 μg m-3 increase in PM2.5
|
RR of mortality is 1.04 with 95% CI: 1.01–1.08 [3] but note unexamined confounding factors could increase uncertainty. |
Passive smoking: Long-term exposure compared to little or no exposure. |
RR of lung cancer [32] is 1.24 with 95% CI: 1.13–1.36
RR of heart disease [33] is 1.23 with 95% CI: 1.14–1.33 Excess mortality risk [36] was based only on heart disease RR of 1.31 and 1.24 for males and females respectively, at the higher end of the range given by [33]. |
Obesity: High BMI compared to "normal" BMI = 24 | Uncertainty in YOLL not presently available. Ref. [26] states that "we were unable to provide confidence intervals for our YLL estimates. We are unaware of any developed analytic formula that would allow easy calculation of SEs and confidence intervals". Uncertainties in relative risks are illustrated in Figure 2. |
Radiation: Risk per unit dose equivalent. | Subjective 95% CI was given for NAS risk analysis [14] where it was stated that "estimates that are a factor of two or three larger or smaller cannot be excluded" (see also [54]). This uncertainty is expected to also apply to the ICRP [15] risk estimates presented here. In particular, it is uncertain whether a DDREF should be applied: if a DDREF was not applied, this would increase the ICRP risk estimates by a factor of 2. |