Safety Requirements And Guidance For Analytical X-ray Equipment - Safety Code 32

1. Introduction

X rays are short-wavelength electromagnetic radiations that can undergo various interactions with matter. Such interactions yield data which, when appropriately analyzed, can provide useful information on the materials irradiated. Machines, typically x-ray diffraction devices and x-ray spectrometers, have been designed to utilize very intense x-ray beams in order to facilitate microscopic examinations or atomic analyses of materials in industry, research laboratories and educational institutions. These machines are generally referred to in this Safety Code as analytical x-ray equipment.

X rays are ionizing radiation that can cause adverse biological effects such as cancer and leukemia. While a brief exposure to the hands in the primary beam of analytical x-ray equipment may not present any clinically observable effects over a short- or long-term period in some individuals, the effect in other individuals may result in mild skin discoloration, which subsequently could develop into a burn, dermatitis and possibly progress to a cancer. Radiation exposures may be considered acute or chronic. Acute exposures are those for which relatively large radiation doses are delivered within short time periods, and the resulting adverse biological effects are manifested in a time frame approximately in an inverse relation to the dose incurred. Chronic exposures are those for which small doses are delivered, more or less uniformly, over long time periods, and the resulting adverse biological effects are more subtle and may develop within years or decades. Recovery from radiation insult depends on many factors including but not limited to, the radiosensitivity of the tissue(s) or organ(s) irradiated, the relative biological effectiveness (RBE) of the radiation, the age and sex of the individual, the dose incurred and the time in which it was delivered. While experimental evidence suggests cellular recovery occurs for low doses incurred over long time periods, such mechanisms may be imperfect, and this could eventually lead to late health effects of radiation such as induction of cancer (carcinogenesis), degenerative diseases (e.g., cataracts), and genetically determined ill-health and developmental abnormalities in the progeny of exposed individuals. Thus, radiation exposure could present immediate and late health effects. In common with other types of man-made ionizing radiation sources used in medicine, industry, research and consumer products, there are potential radiation hazards associated with analytical x-ray equipment.

In recognition of the widespread applications of ionizing radiation to mankind worldwide and the potential adverse human health effects, the International
Commission on Radiological Protection (ICRP 1991)⁽³⁾ has recommended a system of radiological protection which, when followed, would ensure that the risks from ionizing radiation use remain low. The ICRP recommended dose equivalent limits (Appendix I) are based on the prevention of deterministic effects by keeping radiation doses below the relevant threshold, and on the demand that all reasonable steps be taken to reduce the incidence of stochastic effects to acceptable levels. (Deterministic effects are those for which the severity of a biological effect increases with dose; and stochastic effects are those for which the probability of occurrences increases with absorbed dose, but the severity does not depend on the dose.) In this context, analytical x-ray equipment must be designed and constructed to conform with regulatory standards, and persons who install, use and maintain them must know the x-ray hazards inherent with such equipment and adhere to recommended procedures.