1Sv1Hr

Great video at the bottom of this page.
Cosmic Rays Pose Huge Hurdle for Spaceflight
http://dsc.discovery.com/news/2008/04/15/space-cancer-radiation.html
Space Radiation and Cataracts
http://www.uctv.tv/search-details.aspx?showID=8757

Radiation sickness

Radiation sickness is illness and symptoms resulting from excessive exposure to ionizing radiation.

There are two basic types of radiation: ionizing and nonionizing.

    Nonionizing radiation comes in the form of light, radio waves, microwaves and radar. This kind of radiation usually does not cause tissue damage.
    Ionizing radiation is radiation that produces immediate chemical effects on human tissue . X-rays, gamma rays, and particle bombardment (neutron beam, electron beam, protons, mesons, and others) give off ionizing radiation. This type of radiation can be used for medical testing and treatment, industrial and manufacturing purposes, weapons and weapons development, and more.

Considerations

Radiation sickness results when humans (or other animals) are exposed to very large doses of ionizing radiation.

Radiation exposure can occur as a single large exposure (acute), or a series of small exposures spread over time (chronic). Exposure may be accidental or intentional (as in radiation therapy).

Radiation sickness is generally associated with acute exposure and has a characteristic set of symptoms that appear in an orderly fashion. Chronic exposure is usually associated with delayed medical problems such as cancer and premature aging, which may happen over a long period of time.

The risk of cancer depends on the dose and begins to build up even with very low doses. There is no "minimum threshhold."

Exposure from x-rays or gamma rays is measured in units of roentgens. For example:

    Total body exposure of 100 roentgens/rad (or 1 Gy) causes radiation sickness.
    Total body exposure of 400 roentgens/rad (or 4 Gy) causes radiation sickness and death in half the individuals. Without medical treatment, nearly everyone who receives more than this amount of radiation will die within 30 days.
    100,000 roentgens/rad (1000 Gy) causes almost immediate unconsciousness and death within an hour

The severity of symptoms and illness (acute radiation sickness) depends on the type and amount of radiation, how long you were exposed, and which part of the body was exposed. Symptoms of radiation sickness may occur immediately after exposure, or over the next few days, weeks, or months. The bone marrow an