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One of the first studies on the effect of uranium mining on the health
of miners and other workers has concluded that exposure levels in mines
should be reduced. ‘Our findings support moves that are being made internationally
to reduce safe exposure levels even further,’ says Alistair Woodward of
the Department of Community Medicine at the University of Adelaide.

According to current international standards, the acceptable annual
dose limit of radiation for miners is 50 millisieverts. But following research
published in 1989 on the long-term effects of radiation on survivors of
the nuclear explosions at Hiroshima and Nagasaki, the International Committee
for Radiation Protection is considering lowering the limit to 15 millisieverts.
Woodward says that ‘the mining industry is anticipating higher standards.’

At the revised level of exposure, the risk of a uranium miner developing
lung cancer would be well below the risk associated with smoking. The National
Research Council in the US has estimated that nonsmoking uranium miners
who work for 40 years from age 20, and receive an annual dose level of 15
millisieverts, will increase their lifetime risk of contracting lung cancer
from about 11 in 1000 to 15 in 1000. Smokers have a lifetime risk of 250
in 1000.

Lung cancer among uranium miners is caused by exposure to radon gas,
which the ore emits. The miners inhale so-called radon daughters, the short-lived
breakdown products of radon. Leukaemia and skin cancer may also be caused
by radon daughters, but the evidence for this is not as strong.

At Radium Hill, the mine in South Australia studied by Woodward and
his colleagues from the University of Adelaide and the South Australia Health
Commission, radiation levels during the mine’s operation were estimated
to be 250 millisieverts per year. Though this is considered to be relatively
low compared with other mines operating at the time, a significant level
of lung cancer has been detected among the former miners.

Radium Hill, 100 kilometres west of Broken Hill, was operated as an
underground uranium mine by the South Australian Department of Mines from
1952 to 1961, when it closed. About 2600 men and women worked in the mine
or in the nearby processing plant; no women worked underground.

Woodward and his colleagues, David Roder, Tony McMichael, Phil Crouch
and Arul Mylvaganam, traced the incidence of cancer and other diseases among
1661 former workers at the mine, including many who had died, until the
end of 1987.

The study, one of the first to investigate the fate of uranium miners
who received comparatively low doses of radiation, will be published next
month in the journal Cancer Causes and Control.

At Radium Hill, lung cancer was more prevalent among those who worked
underground, increasing their risk of lung cancer threefold. Overall, the
risk of lung cancer was 1.14 to 1.94 times greater than for the normal population.
According to Woodward, the risk doubled for every 38 months of work at the
mine. The findings held true even when allowance was made for smoking habits,
the number of workers who could not be traced, and occupational factors
other than radiation exposure. Woodward stresses that the findings are not
alarming but they do clearly indicate an increased risk.

Anecdotal evidence collected by the researchers suggests that the miners
were largely oblivious to the risk. A group of Irishmen, unused to the hot
Australian climate, went down the mine for their drinking sessions.

But the study confirms earlier research among miners that showed that
lung cancer is by no means the main cause of death. It was responsible for
9 per cent of the deaths among former Radium Hill workers. Death from accident
was more common as was violent death away from the mine, including homicide.
‘The excessive number of deaths of this kind among mining populations has
been ascribed to lifestyle rather than work,’ Woodward writes in the June
issue of Search, the journal of the Australian and New Zealand Association
for the Advancement of Science. ‘Little attention has been paid to whether
lifestyle is affected by the location and nature of the work.’ Woodward
describes Radium Hill as an ‘isolated and inhospitable place’.

Researchers in the US have also looked at the records of uranium miners
who received exceptionally high doses of radiation. In 1988, the US Committee
on the Biological Effects of Ionising Radiations reported that rates of
lung cancer among uranium miners who worked at mines in Colorado in the
1940s and 1950s were up to 20 times higher than among the normal population.
According to Woodward, writing in Search, between 50 and 75 per cent of
the deaths among underground workers in the pitchblende mines of central
Europe in the 1920s resulted from lung cancer. Exposure to radon was the
chief cause.

Today, with constant monitoring of exposure levels, mining companies
claim that they have reduced substantially the risk among miners. At Olympic
Dam at Roxby Downs in South Australia, uranium miners are subjected to less
than one-tenth of the radiation received by underground miners at Radium
Hill. Woodward reports that the average annual dose at Olympic Dam is about
19 millisieverts. At the Ranger uranium mine in the Northern Territory,
opencast mining is said to allow sufficient natural air movement to keep
radon exposure at safe levels. Also, the mill is ventilated to control airborne
contaminants. All the work areas are routinely checked for radioactive dust.