How many Xrays are safe?

Have you ever wondered how many X-rays are safe in a year? When your doctor orders an occasional X-ray, you probably focus on the findings, not the amount of radiation you’ll be exposed to. But if you need numerous tests, you may wonder if you’re getting too much radiation exposure and how it might affect you. The concern about radiation exposure is an increased risk for developing cancer later in life. Ionizing radiation from tests such as X-rays has the potential to damage tissue in the body, including cell DNA. In this blog post, we will explore the safety of X-rays and how many are considered safe in a year. 

Lets learn about the unit of measurement first.

The radiation dose absorbed by a person (that is, the amount of energy deposited in human tissue by radiation) is measured using the conventional unit rad or the SI unit gray (Gy). The biological risk of exposure to radiation is measured using the conventional unit rem or the SI unit sievert (Sv). To determine a person’s biological risk, scientists have assigned a number to each type of ionizing radiation (alpha and beta particles, gamma rays, and x-rays) depending on that type’s ability to transfer energy to the cells of the body. This number is known as the Quality Factor (Q).

When a person is exposed to radiation, scientists can multiply the dose in rad by the quality factor for the type of radiation present and estimate a person’s biological risk in rems. Thus, risk in rem = rad X Q. Lets leave the calculation part to those scientists and skip to the radiation exposure we are taking about.

One dental x-ray =  0.05 mSv

One chest x-ray = 0.1 mSv

One mammogram =  0.7 mSv

One CT scan(depending on organ) = 1 to 15 mSv

According to Radiation Protection Act, 

The limit value for the effective dose aimed at protecting members of the public is 1 millisievert in a calendar year. (e.g. resulting from the release of radioactive substances from nuclear facilities). 1mSv = 10 × 0.1 mSv = 10 Chest Xrays.

The limit value for the effective dose in order to protect occupationally exposed persons is 20 millisieverts in a calendar year.

Lifetime occupational exposure must not exceed 400 millisieverts.

For women of childbearing age, the organ equivalent dose (organ dose) for the uterus must not exceed 2 millisieverts per month.

For pregnant women, the limit value for the unborn child is 1 millisievert from the time of declaration until the end of pregnancy. (10 ChestXrays)

The limit values for the organ equivalent dose ("organ dose") for the general public are specified in the Radiation Protection Act. They are equal to 15 millisieverts in a calendar year for the lens of the eye and 50 millisieverts in a calendar year for the skin.