Radiation

Investigating the Health and Safety of Ultrasound and Infrasound

Ultrasound has been used successfully for many years for a range of applications including health protection, the diagnosis, investigation and treatment of disease and for many industrial applications. These developments have stimulated a great deal of research into the effect of ultrasound on living tissue and other material and have led to increasingly sophisticated medical scanning, treatment techniques and equipment design. Infrasound has been less well investigated but it can, under some circumstances, present a potential hazard to health so needs further scientific investigation.

 

In 2005 the Agency's remit covering non-ionising radiation (NIR) was extended to include ultrasound and infrasound. Examining the health aspects of ultrasound and infrasound is a new role for the Agency.

 

Gathering expertise and information

Ultrasound is a specialised area covering a wide range of medical and non-medical applications, and it was clear that specialist information was needed in order to assess the likely importance and extent of health and safety issues. A workshop was organised with invited international experts covering a range of ultrasound and infrasound topics and applications, held in collaboration with the International Commission on Non-Ionizing Radiation Protection (ICNIRP), with support from the Department of Health.

It brought together experts from different disciplines, including medicine, epidemiology, medical physics, biophysics, biology and engineering to provide reviews and discuss what is known about possible adverse health effects and provide overviews of technological advances both in medicine and in industry. It is clear that ultrasound has become an essential tool in medicine, capable of providing high quality images and a potentially important non-invasive surgical tool.

Ultrasound in medicine is familiar to most people because it is used to scan unborn babies. Where it is used by trained medical staff, there are clear benefits to the unborn baby and to the mother. Over the years it has developed into a routine procedure that has found widespread acceptability, as well as enthusiasm for its use among parents-to-be, manifested in the commercial availability of ultrasound photographs and videos. But it is important to continue research towards improving the quality of information obtained from ultrasonic scanning while minimising any possible harmful exposure.

The Agency's independent Advisory Group on Non-ionising Radiation (AGNIR) was also asked to review the epidemiological and biological evidence for possible adverse health effects of ultrasound exposure. This review is currently in progress.

The use of high intensity ultrasound for medical treatment is an exciting and rapidly developing area. Clinical trials are underway to investigate its benefits including accelerating bone repair, treatment of soft tissue injuries, and cancer treatment. Another area of research is its use in improving drug and gene therapy.

In addition, ultrasonically powered tools are used in dentistry and surgery. The safety implications of using high intensity ultrasound in surgery and to treat medical conditions are clearly very different from those for diagnostic ultrasound. For these high power devices the concerns, apart from operator safety, are mainly for accurate targeting of the ultrasound whilst avoiding any damage to other tissues. Research studies and clinical trials are underway to evaluate this.

Ultrasound, often of high intensity, is used extensively for non-medical applications in industry including; materials testing, fault location, cleaning, drilling and welding. One of the most exciting fields in current research on industrial applications is sonochemistry. Here, processes and techniques are being developed that can be used in environmental protection, materials processing and food technology. Where high intensity ultrasound is being used it is important that we assess any risks to ensure the safety of those operating equipment.

Adverse health effects associated with exposure to infrasound and low frequency noise are less well understood, but concerns exist about the safety of these acoustic waves. While adverse health effects are unlikely at levels normally experienced in the environment, it is important to establish if exposure below hearing thresholds at these low frequencies can cause damage.

 

The way ahead – an evidence based approach

We will continue to work with external experts and will carefully assess the information obtained from our workshop and the AGNIR's review of the evidence for possible adverse health effects of ultrasound exposure. We will consider what actions are required on the basis of the evidence for harm and what programme of work within the Agency and elsewhere would most effectively tackle this. We will also continue to work with our international partners in relation to the development of exposure guidelines and collaborative research.

 

New Personal Dosimetry Systems

The Agency promotes the health of radiation workers by providing services which help employers fulfil their health and safety obligations. We provide radiation protection advice and training, instrument testing, and the routine assessment of radiation doses received by individual workers.

Individual doses are assessed using radiation dosemeters, often called "radiation badges", which are worn for a fixed period and returned to the issuing laboratory for processing. The Agency's Personal Dosimetry Service (PDS), part of the Centre for Radiation, Chemical and Environmental Hazards, operates several services which assess doses from gamma-, beta- and X-radiations, from neutrons and from radon. The PDS uses body "badges" and extremity dosemeters, which measure doses to the fingers. The service covers approximately 60,000 workers at 4,500 separate employer sites in the medical, dental, veterinary, industrial and research sectors.

 

We are currently completing a project to replace the system which issues and processes thermoluminescence dosemeters (TLDs). TLDs account for the majority of dosemeters issued by the Personal Dosimetry Service. They work by storing the energy received from the ionising radiation until they are heated (to 250° C) when the energy is released as light, which is collected and measured. These operations are performed in automated readers linked to sophisticated computer systems. Since 2000, the availability of new luminescence materials and the need to measure lower occupational doses has led to important innovation and change.

The change covers both the method of heating and the TLD material used, which provides higher reader reliability and the assessment of smaller doses for both whole body and extremities. New automatic readers have been commissioned and new finger and body dosemeters designed. In the case of the extremity dosemeter, we worked with suppliers and a number of other UK dosimetry services to promote design and type-testing.

The different characteristics of the new thermoluminescence material meant a modified design was needed for the plastic holders used for the body TLD cards. The new design, which will be used exclusively by the Agency, has now been developed for testing.

Clients started using the new extremity dosemeter during the first half of 2006, and the new body TLD system will be launched in October 2006.

 

Radiation and Leukaemia

It is well documented that high doses of radiation increases the risk of leukaemia in people; however it remains uncertain whether effects also occur at very low doses. Epidemiological studies may not be sensitive enough to detect radiation effects at low doses so specialist knowledge on the effects of radiation on the DNA within certain cells in the body (stem cells) is required.

Staff in the Radiation Protection Division have, for some years, been studying the mechanisms of radiation-induced leukaemia, specifically acute myeloid leukaemia and have published scientific papers which identify specific genes that are either triggers for leukaemia or make people more likely to develop leukaemia if they carry that particular gene. The effects on the cell of mutations in one key gene are being studied in collaboration with colleagues at the Centre for Infections.