快猫短视频

GUIDELINES have been drawn up to prevent nurses being exposed to unacceptable
levels of radiation by patients. The guidelines come as another study suggests
low levels of radiation may pose unsuspected dangers.

Every year, thousands of people worldwide are given iodine-131 to treat
overactive thyroid glands and thyroid cancer. Their thyroid glands become
radioactive and pose a health risk to anyone who is close to them for long
periods, especially their partners
(快猫短视频, 28 August 1999, p14).

If these patients need constant care, they also pose a risk to nurses. Claire
Greaves and Wendy Tindale at Sheffield鈥檚 Northern General Hospital have
calculated that on just the second day of looking after a patient who has taken
iodine-131, a nurse will have received a radiation dose of up to 1.3
millisieverts. British safety guidelines state that members of the public should
not receive more than 1 millisievert a year.

Greaves and Tindale have now drawn up rules to ensure nurses receive less
than 0.5 millisieverts. They include limiting shifts to six hours in the two
days after the patient is given iodine-131, and each nurse doing one shift only.
When they put the scheme into practice, dose meters worn by nurses clocked up no
more than 0.25 millisieverts.

Patients who die shortly after receiving radio-iodine treatment also pose a
risk to mortuary staff, Greaves adds. In extreme cases, she thinks there should
be a delay of two weeks before doing the post-mortem, to avoid exposing the
pathologist to radiation and contaminating the lab.

Michael Clark, a spokesman for Britain鈥檚 National Radiological Protection
Board, welcomes the report. 鈥淲e need to make sure that all hospital
staff鈥攅specially nurses鈥攁ppreciate the potential problems with such
patients.鈥� He stresses, however, that the risks to health are probably very
low.

But the risks of low-level radiation might be greater than we realise.
Estimates are mainly projections from the cancer incidence in survivors of the
atomic bomb blasts in Hiroshima and Nagasaki, where levels of radiation were
very high. 快猫短视频s assume that cell damage falls off in direct proportion to
the radiation dose.

However, this may be over-optimistic, because it turns out that a single
alpha or beta particle can damage a whole group of cells. In this week鈥檚
Proceedings of the National Academy of Sciences (vol 98, p 14,410),
scientists in the US showed that when 10 per cent of a group of cells were
targeted by radioactive alpha particles, the damage to their DNA somehow spread
to neighbouring cells, causing the same amount of damage overall as when all the
cells were targeted.