How much radiation can cause health problems?

How much exposure to radiation will it take for negative effects on your health/life to happen? Is it worse if you yourself are exposed to the radiation or if you, say, eat or drink something that has been exposed to radiation? Is exposure to things giving off radiation like computers, photocopy machines, TV and the like, or consuming something (food, drink) placed dangerously near them while they're on anything to worry about?

Radiation is only dangerous on high scales. While I wouldnt reccomend standing in front of a high powered large microwave...Things like copy machines, radios and cellphones are very small in amount and unless deliberately exposing yourself to large quanities, they should be nothing to worry about. Food and the like can also get exposed to radiation, but lets be real. Unless you zap a burger with some gamma rays, it's not gunna be unhealthy.

A good example is when you go to the dentist and he puts what seems to be a suit of armor on you. ya know, that big heavy blanket. He puts that right over you. This is actually concentrated at your genitals. Seriously, because those are sensitive to radiation and can mess up things.

Any way, using the above example...Think about it. he's getting a close up of your teeth. Teeth that are very close to your head. The radiation is not damaging in quick intervals.

Time and Power are the most important things to worry about.

Hundreds of curies, I trust.

All things emit these peskie radicals.

We do not have to worry.

We all need to rejuvenate every now and then

Ionizing radiation has many uses. An X-ray is ionizing radiation, and ionising radiation can be used in medicine to kill cancerous cells. However, although ionising radiation has many uses the overuse of it can be hazardous to human health. Shop assistants in shoe shops used to use an X-ray machine to check a child's shoe size, which would be a big treat for the child. But when it was discovered that ionising radiation was dangerous these machines were promptly removed.

The worry is more dangerous than radiation. People are exposed to vast amounts of radiation in cancer therapy. Radiation will begin to reduce the bodies immune system. I believe radiation has an accumulative effects on the body. Humans have high resistance to radiation due to many generations of living in solar extreme zones. So don't worry. Compare solar radiation to artificial sources. Electromagnetic radiation is also something to be avoided. I wouldn't have an office next to the companies transformer for the building.
I heard of a guy who died young of a brain tumor. He slept under a large electrical conduit which ran over the bunk bed near his head.

Effects
All of these units are meaningless until one has some idea of how bad one of them is for you. Here are some rules of thumb that may be off by factors of two from one case to the next:

Instant Death: It takes a monumental radiation dose to kill outright, typically something like 5000 R (50 Grays) ``whole-body'' - i.e. half a million ergs of energy deposited in every gram of your body. This amount of energy wipes out your central nervous system (CNS) immediately when delivered all at once. Needless to say, only the military mind makes a strong distinction between this and the next level down.
Overnight Death: Approximately 900 R (9 Grays) whole-body will accomplish the same thing as 50 Grays but it takes about a day.
Ugly Death: A somewhat lower dose, around 500 R (5 Grays) causes severe ``radiation sickness'' (i.e. nausea, hair loss, skin lesions, etc.) as the body's short-lived cells fail to provide new generations to replace their normal mortality (``cell reproductive death''). It is not this trauma which usually kills, however, but the complications that arise from a lack of resistance to infection, due in turn to the lack of new generations of white blood cells. If you survive the initial radiation sickness and avoid infection, you will probably recover completely in the short term; but you are very likely to develop cancer (especially leukemia) in later years (usually some 10-20 years later!) and your offspring, if any, will have a high probability of genetic mutations.
Sub-Acute Exposures: From a whole-body dose of around 100 R (1 Gray) delivered in less than about a week, you are unlikely to notice any immediate severe symptoms. However, you are likely to develop leukemia in 10-30 years, and there is a significant chance of genetic mutations in your offspring. A whole-body exposure of 5 R delivered over 1 year was believed in 1970 to represent 1.8 ``doubling doses'' -- i.e. it was thought to multiply your odds of developing cancer by a factor of 2.8 if maintained year after year. At that time it was also the legal exposure limit for radiation workers in the U.S.A., set by the Atomic Energy Commission (AEC) there. Presumably quite a few people received this exposure for a few years, although it is unusual for more than a small fraction of workers to receive the maximum allowed exposure. For perspective, it is noteworthy that a series of spinal X-rays is apt to give an exposure of 1-4 R locally, and that an afternoon on Wreck Beach in midsummer often produces a painful sunburn that represents 10-20 R to the skin; the resultant burn is a bona fide radiation burn and is just as dangerous as any other kind! In fact, the overwhelming majority of all radiation-induced cancer fatalities on Earth can be attributed directly to far ultraviolet from our favourite nuclear fusion power plant in the sky: the Sun.
Marginal Exposures: The average exposure from natural sources of radiation is on the order of 300 mR per year. As of 1979 this was also the Canadian legal limit for public exposure from artificial sources. Whether an extra 300 mR makes a significant difference epidemiologically in the incidence of cancer depends almost entirely on what one considers significant; however, it is a fact that the statistical difference between populations that have received such an exposure ``artificially'' and those who have not is smaller than the statistical differences between populations with different eating habits, who live in different regions, who have different types of jobs, etc. This is partly because of the wide variety in the amount and type of natural radiation exposure.