What is the Safe Level of Ionizing Radiation?

Ionizing radiations are a big part of our life now. Medical and power generations are two main fields where ionization radiations are put to useful work.

X-rays use to make x rays of broken bones, CT scans of the brain, chemotherapy to treat cancer patients and other operations like this are some of the examples of positive utilization of ionizing radiations.

On the other hand, these radiations are extremely dangerous and any exposure can be life-threatening. So the question is “What amount of these ionizing radiations can be considered safe?”

Source of Ionizing Radiation

Ionizing radiation can be emitted or generated by several sources including natural or manmade. Almost all sources of radiation can be very dangerous for humans but radiation emitted from radioactive material like uranium is especially very dangerous.

So to define a safe limit of ionizing radiation exposure it is very important to define the source of radiation and how an individual can get exposed to it.

– Radioactive Material

Materials like uranium are naturally radioactive and will emit ionizing radiation during their entire life span. Engineers working in atomic power plants can get exposed to these radiations. The chances of the general public getting exposed to this radiation are very less.

– Artificial Radiation

Ionizing radiation generated by electrical equipment for medical treatment can be dangerous if exposed for an extended period. Health radiography works are highly exposed to them but it can be avoided by some simple precautions.

– Cosmic Radiations

Most of the ionizing radiations coming from outer space are blocked by the earth’s ozone layer but some that pass through it can be dangerous if exposed for a longer period. It is the most dangerous type of radiation when considering the number of people that can be exposed to it.

What are Different Units of Measuring Ionizing Radiation?

It’s important to know the measuring unit of radiation because we will express the radiation safe level in this unit reading. There are some units but in the case of the safe radiation level, we commonly use Sievert.

1. Becquerel (Bq)

Becqere Bq is the international unit to measure the ionizing radiation-related by a radioactive material upon decomposing. Another unit used for this is Curie (Ci is a USA based unit)

2. Coulomb/Kilogram (C/kg)

It is an international unit used to measure the amount of radiation traveling through the air. Apparatus is available for measuring radiation traveling through air. Another unit for this is Roentgen (R is a USA based unit)

3. Gray (Gy)

Gray Gy is the international unit to measure the ionizing radiation absorbed by an object. Another unit used for this is Rad (USA based unit) and one gray is equal to 100 rads

4. Sievert (Sv)

It is the international unit used to measure the ionizing radiation absorbed by an object based on the type of radiation received and its effect on a particular organ. Another unit for this is rem (USA-based unit) and one Sievert is equal to 100 rems.

What are the Safe Radiation Levels per Year for Humans?

As recommended by the United State of America federal agency, the maximum safe limit of ionizing radiation exposure by natural sources (that are mostly by cosmic radiation and radon) is limited to 300 millirems per year.

The 300 millirem limit of radiation exposure is for those people living on the sea level area. People living in areas that are considerably higher than sea level have a limit of about 400 millirems of exposure per year.

This safe limit is also effect by the weight of the person. For any diagnostic tracer, one microcurie of calcium 45 (a radioactive material given orally) is given to a person weighing about 100 ponds then the dose of 3.7 is recommended and for a 200-pound person, it reduces to 1.85 millirems.

The Safe Limit of Ionizing Radiation Exposure in the Gestation Period

If in any case when a pregnant woman has to be exposed to ionizing radiation, then as per federal regulation of the United State of America the dose of radiation cannot exceed the value of 500 millirems during the complete gestation period. There is also a monthly limit of 50 millirems.

The Safe Limit for Lifetime Ionizing Radiation Exposure

To set a safe limit of ionizing radiation exposure for the entire life span of a human, the federal regulation of the United State of America limited ionizing radiation exposure to 1000 millirem multiple of the year of its age.

This means if a human live for 60 years then the lifetime exposure to ionizing radiation cannot exceed 60,000 millirems. This includes occupational radiation exposure (radiation exposure during work), natural radiation exposure due to cosmic radiation, and radiation exposure during any medical procedure.

A Safe Level of Ionizing Radiation Exposure for Adults

According to USA federal occupation agency, ionizing radiation exposure for any age of people should be kept as low as possible. For an adult, the maximum ionizing radiation exposure done per year should not exceed 5000 millirems.

This 5000 millirem is the exposure limit for workers handling radiation-related processes and does is of radiation emitted by natural sources like radioactive material or medical work equipment. This 5000 millirem dose is above the standard 300 millirem dose that anyone can get from a natural radiation source or a medical procedure.

The Safe Level of Ionizing Radiation Exposure for Minors

Any person with age under 18 years and working on a site or job that handles radioactive material or ionizing radiation has a maximum exposure limit of 500 millirems.

This 500 millirem is directly extracted from one-tenth of the maximum recommended exposure limit for adults. This 500 millirem dose is above the standard 300 millirem dose that anyone can get from a natural radiation source or a medical procedure.

The Safe Level of Ionizing Radiation Exposure for Astronauts

Astronauts are highly exposed to cosmic radiation in outer space as there is no ozone layer for protection. The highest recommended level of cosmic radiation exposure for astronauts was 25000 millirems per year till 1950.

After that, it was reduced to 15000 millirems in 1950 and then was further reduced to 5000 millirems in 1957. This radiation done is beyond the 300 millirems dose recommended for medical purposes or by any natural source.

References

EPA, United State Environmental Protection Agency, Radiation Terms and Units link [https://www.epa.gov/radiation/radiation-terms-and-units]

MIT, Massachusetts Institute of Technology Radiation, how much is considered safe for humans? Link[https://news.mit.edu/1994/safe-0105]

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