Legal Dose of Radiation

PPE is equipment worn to minimize exposure to hazards that other workplace controls, including engineering controls, administrative controls and safe work practices, cannot control. In the event of a radiological emergency, PPE does not protect workers from most types of direct external exposure. However, the correct use of appropriate PPE helps to prevent or minimise internal exposures by preventing the absorption, inhalation or ingestion of radioactive substances through the skin. The radiation doses discussed above in the Dose Limits for Emergency Response section would then consist primarily of direct and external exposure to radiation – just as an X-ray causes radiation exposure. Direct external exposure may pose a persistent hazard in the event of a radiological emergency. Generally, the type of PPE required and the guidelines for use are based on the level of contamination. The dose limits established in 10CFR20 are based on the general recommendations of the ICRP and NCRP (section B.7) that the total effective dose to an individual (see Chapter 22, Section B.7) should not exceed 50 mSv (5 rem) per year. In addition, 10CFR20 requires that the deep dose (dose equivalent to a depth of 1 cm in tissue) for a single organ or tissue (excluding the lens) not exceed 500 mSv (50 rem) per year. The limit for shallow dose equivalent (dose equivalent to a depth of 0.007 cm in tissues) for the skin and extremities is also 500 mSv (50 rem) per year. The most restrictive limit applies to the lens of the eye, which has an annual limit of 150 mSv (15 rem).

The annual workplace dose limits for minors (<18 years) are 10% of the annual dose limits for adult workers. The dose equivalent to that of an embryo or foetus should not exceed 5 mSv (0.5 rem). The limit values for the equivalent organ dose ("organ dose") for the general public are laid down in Article 80(2) of the Radiation Protection Act. They correspond to 15 millisieverts in a calendar year for the lens of the eye and 50 millisieverts in a calendar year for the skin. Although radiation can cause local injury (e.g., to hands and arms), whole-body exposure is more likely in the event of an incident involving a nuclear detonation or improvised nuclear device (IND), radiological propagation device (RDD), radiation exposure device (RED) or any other emergency described on this page. While ARS is generally expected at absorbed doses around 70 rad (0.7 Gy), mild symptoms can be observed at doses as low as 30 rad (0.3 Gy).4 Doses ≥100 rad (≥1 Gy) are also doses where an increased risk of acute death is a problem. At these and lower doses, the signs and symptoms of ARS may be non-specific and difficult to distinguish from other diseases and injuries, especially in situations where detection of radiation exposure is delayed. In addition to keeping the radiation dose below the above limits, work with ionizing radiation sources must be planned and carried out in such a way as to keep doses as low as reasonably achievable. The RDRC provides a convenient way to approve research involving radioactive drugs that are not approved by the FDA when used under certain conditions.

The FDA`s dose limits for RDRC approval are similar to federal and state occupational dose limits and typically allow PET studies to be conducted using novel radiotracers using C-11, N-13, O-15, and F-18. However, with the advent of PET/CT scanners and the requirement to include all X-ray procedure doses that are part of the research, FDA dose limits can be quickly exceeded if the protocol includes multiple scans. Similarly, with paediatric dose limits set at 10% of those for adults, it is very difficult to conduct PET/CT studies in children under the RDRC. Depending on the nature of the reaction operations performed by a given worker, the worker may require different types of PPE to protect against hazards other than radiation contamination. OSHA requires employers to select and provide appropriate PPE to their employees and ensure that it is used correctly. When workers provide their own protective equipment, employers are always responsible for ensuring its adequacy, proper maintenance and decontamination. Both the ICRP and NCRP work towards the overall goal of achieving radiation doses «as low as reasonably achievable.» The standards are not intended to license exposure circumstances and radiation doses at the standard level. Within minutes, hours and days immediately following radiation exposure, health care providers should monitor victims for signs and symptoms of acute radiation syndrome or acute radiation sickness (AIS). Emergency responders and employers should monitor themselves and others for signs and symptoms of RAS as described below. Report any signs of SIA to your team leader, supervisor or other appropriate employee.

20,000 Therapeutic treatment with radioactive iodine of the thyroid gland. A localized dose delivers 10,000,000 millirems to the thyroid gland and about 20,000 millirems to the rest of the body. A dose of radiation to kill a cancerous tumor often sends a beam that delivers 6,000,000 millirems to the cancerous tissue, but the equivalent dose of the whole body is much less, as in the case of the thyroid gland. Dose limits are not a dividing line between hazardous and harmless exposure. Exceeding a limit means that the probability of health effects (especially cancer) exceeds a value defined as acceptable. Limit values are set by the legislator or regulatory authority. 5.5.4. A woman shall not be declared pregnant unless she so states in writing without compulsion. Unless a woman declares her pregnancy, she should be treated like any other radiation worker. Employers are still required to protect workers from these and other recognized health and safety risks. The Additional Resources page contains information from other organizations on the hazards associated with radiological emergencies and how to protect workers from accidents and related occupational diseases. The skin equivalent dose limit should be applied at the average dose over any area of 1 cm2, regardless of the area exposed.

The U.S. federal government sets dose limits for radiation workers and the general public. The federal agency that enforces radiation protection legislation and dose limits is the Nuclear Regulatory Commission (NRC). Dose limits are listed in NCRP publications. NCRP Report No. 116, Limitation of Exposure to Ionizing Radiation (1993), provides the most up-to-date information on occupational and non-occupational dose limits.1 A summary of Report No. 116 is provided in Table 1-3. These dose limits do not apply to medically exposed patients for diagnostic or therapeutic purposes. The annual effective dose limit for occupational exposure is 5 rem (50 mSv) per year. The cumulative effective dose limit for occupational exposures is as follows: For members of the public, the annual effective dose limit equivalent is 1 mSv (0.1 rem).