Radiation protection

[1] Exposure can be from a source of radiation external to the human body or due to internal irradiation caused by the ingestion of radioactive contamination.

Ionizing radiation is widely used in industry and medicine, and can present a significant health hazard by causing microscopic damage to living tissue.

For low level exposures there can be statistically elevated risks of radiation-induced cancer, called "stochastic effects" due to the uncertainty of them happening, conventionally indicated by the unit sievert.

The ICRP recommends, develops and maintains the International System of Radiological Protection, based on evaluation of the large body of scientific studies available to equate risk to received dose levels.

[2] The ICRP's recommendations flow down to national and regional regulators, which have the opportunity to incorporate them into their own law; this process is shown in the accompanying block diagram.

In most countries a national regulatory authority works towards ensuring a secure radiation environment in society by setting dose limitation requirements that are generally based on the recommendations of the ICRP.

ALARP is an acronym for an important principle in exposure to radiation and other occupational health risks and in the UK stands for As Low As Reasonably Practicable.

This policy is based on the principle that any amount of radiation exposure, no matter how small, can increase the chance of negative biological effects such as cancer.

It is also based on the principle that the probability of the occurrence of negative effects of radiation exposure increases with cumulative lifetime dose.

[13] Age is a significant factor in risk associated with CT scans,[14] and in procedures involving children and systems that do not require extensive imaging, lower doses are used.

Common types of wearable dosimeters for ionizing radiation include:[16][17] Almost any material can act as a shield from gamma or x-rays if used in sufficient amounts.

For example, a practical shield in a fallout shelter with ten halving-thicknesses of packed dirt, which is roughly 115 cm (3 ft 9 in), reduces gamma rays to 1/1024 of their original intensity (i.e. 2−10).

Graded-Z shielding is a laminate of several materials with different Z values (atomic numbers) designed to protect against ionizing radiation.

Personal protective equipment (PPE) includes all clothing and accessories which can be worn to prevent severe illness and injury as a result of exposure to radioactive material.

The respiratory protective equipment described below are designed to minimize the possibility of such material being inhaled or ingested as emergency workers are exposed to potentially radioactive environments.

This scientific advancement allows for the development of a new class of relatively lightweight protective equipment that shields high concentrations of bone marrow to defer the hematopoietic sub-syndrome of acute radiation syndrome to much higher dosages.

One technique is to apply selective shielding to protect the high concentration of bone marrow stored in the hips and other radio-sensitive organs in the abdominal area.

These instruments will normally give a local alarm, but are often connected to an integrated safety system so that areas of plant can be evacuated and personnel are prevented from entering an air of high airborne contamination.

The UK National Physical Laboratory publishes a good practice guide through its Ionising Radiation Metrology Forum concerning the provision of such equipment and the methodology of calculating the alarm levels to be used.

In the United Kingdom the HSE has issued a user guidance note on selecting the correct radiation measurement instrument for the application concerned.

[27] When the intensely ionizing particles found in space strike human tissue, it can result in cell damage and may eventually lead to cancer.

On uncrewed spacecraft in high-electron-dose environments such as Jupiter missions, or medium Earth orbit (MEO), additional shielding with materials of a high atomic number can be effective.

[27] In a 2002 NASA study, it was determined that materials that have high hydrogen contents, such as polyethylene, can reduce primary and secondary radiation to a greater extent than metals, such as aluminum.

Hawks, a graduate of Columbia College, of his severe hand and chest burns in an x-ray demonstration, was the first of many other reports in Electrical Review.

[30] Many experimenters including Elihu Thomson at Thomas Edison's lab, William J. Morton, and Nikola Tesla also reported burns.

Elihu Thomson deliberately exposed a finger to an x-ray tube over a period of time and experienced pain, swelling, and blistering.

[31] As early as 1902 William Herbert Rollins wrote almost despairingly that his warnings about the dangers involved in careless use of x-rays was not being heeded, either by industry or by his colleagues.

He also stressed that "animals vary in susceptibility to the external action of X-light" and warned that these differences be considered when patients were treated by means of x-rays.

Before the biological effects of radiation were known, many physicists and corporations began marketing radioactive substances as patent medicine in the form of glow-in-the-dark pigments.

By the 1930s, after a number of cases of bone necrosis and death of radium treatment enthusiasts, radium-containing medicinal products had been largely removed from the market (radioactive quackery).