Exposure to EMF radiation

During use mobile phones and cord-less phones emit RF radiation. Other sources of the radiation are mobile phone base stations, Wi-Fi access points, lap tops and tablets. The exposures to RF radiation can be long-term or round-the -clock.  Cancer risks of radio-frequency radiation [RF] emitted by some devices in the frequency range of 30 kHz -300 GHz was also evaluated by the IARC for any possible risk for head and brain tumours. It was found that it is Group 2B – a possible human carcinogen. The data based on animal studies and epidemiological studies.

It is important that ambient levels of RF radiation in different locations should be measured to address the public health concern of RF radiation.  International Commission on Non-Ionizing Radiation Protection [ICNIRP] standards are implemented by the industry to ensure public safety. However, as of now, the standards are based on thermal effects of RF radiation and non-thermal biological effects [stochastic] to the brain as a target organ are not considered. 

The guidelines provided by ICNIRP, the threshold level for behaviour changes in animals quoted is not a clear line between safety and hazard. It only indicates that EMF exposure below the threshold is safe. However, it is not correct to assume that above the given level the exposure is harmful. A safety factor of 10 is applied to the threshold level to obtain the occupational exposure limit. A safety factor of 50 is applied to obtain the guideline limit for the general public.

The Radio-frequency fields (measured in the units of microwatts/cm²) are generated by most of the mobile towers and modern wireless gadgets. The mobile towers catering to the upcoming 5G system for seamless connectivity will emit enhanced levels of RF fields, which will be of major public health concern. 

References

Hardell, L., WHO, Radiofrequency radiation and health – a hard nut to crack [review], Int. J. of Oncology, 51, 2017, 405-413

ICNIRP EMF Guidelines for limiting exposures to time-varying electric, magnetic and electromagnetic fields-up to 300GHz, Health Physics, 74 [4], 1998, 494-522 [Being revised]

ICNIRP EMF Guidelines for limiting exposures to time-varying electric and magnetic fields, 1Hz-100kHz, Health Physics, 99[6], 2010, 818-836

Radiological safety in application of radiation in medicine

Positron Emission Tomography (PET)  is used as an imaging technique in a wide range of biomedical research applications in human patients and volunteers. Millions of PET scans are performed worldwide. Radio-tracer is introduced to the patient and its movement or deposition in the body is followed through a PET scan. A typical nuclear medicine procedure results in a radiation dose of around 25 mSv to a patient, while a CT scan using X-rays gives a dose of 5-8 mSv per scan, depending on which part of the body is scanned. To put risks in a proper perspective, natural background radiation dose is in the range of 2 to 3 mSv in year.

Radiation protection principle recommends optimization of the procedure to minimise patient dose. Some of possible ways of minimization of the dose is:

Ø Use highly sensitive and faster scanners for the procedure so that time spent is minimum for scanning so that the system can detect and perform scans at very low levels of emissions

Ø Optimise the radio-tracer dose to the patient to get a good scan

Ø Select a most suitable short-lived low energy photon emitting radiotracer

Ø Minimise radiation exposures of the healthy tissues/organs which are adjacent to the tissue/organ being scanned or treated. 

  

The procedures results in radiation dose (occupational exposures) to the medical, para-medical staff and technicians who are handling the radioactive material and who operate the machines for scanning. Scattered radiation from the primary beam is of concern, particularly to the eye lens, and needs to be monitored. Suitable radiation dosimetry technique should be used for the purpose. The hospital health physicist should ensure that the occupational exposures should be controlled and kept as low as reasonably achievable (ALARA).

Finally, the hospitals, the physicians/radiologist should avoid misuse of this technology for financial gains alone. In addition to the benefits to the patient from the procedure, the patients should be thoroughly briefed about the possible health effects from the exposure to radiation. Benefits should outweigh the risks of the exposures. 

NORM waste disposal needs to be regulated!

Waste containing Naturally Occurring Radioactive Material (NORM) is generated in industries which handle uranium and thorium containing raw materials. The waste contains radioactive uranium/thorium and their progeny and or K-40 which are naturally present in the earth crust in rocks, in ores/minerals and in coal. After recovery of the useful product elements, the waste contains traces of radioactive elements and can pose an environmental hazard. The fly-ash (waste product after burning of coal) also contains radionuclides in more concentrated levels as compared to their presence in coal. The ash waste is used to make bricks in some countries. The constraint is the emanation of radioactive radon gas from the traces of Ra-226/224 present in the fly ash.

There are regulatory limits on the radioactivity elemental concentration levels for disposal without any controls. However, in most of the industrial situations the activity concentration levels are much higher and are not safe to indiscriminate disposal in the environment. Disposal as road fillings is one of the uses of NORM waste.

It is time that national regulatory bodies wake up this public health concern and enforce appropriate controls on the disposal of the NORM waste.

Lung cancer fatality risk and smoking habits

It is well known that there is a strong relationship between the smokers and the incidence and lung cancer fatality. A US lung cancer mortality study indicated the mortality rate increased with age and the number of fatalities from lung cancer among smokers increased very significantly as compared to non-smokers.

Mortality rate per 100,000 person-years

Age group                Non-smokers          Smokers

55 – 59 y                   5.3                              206

60 – 64 y                   11.6                           361

65 – 69 y                   21.5                           581

70 – 74 y                   34.9                           909

It is indicated that the incidence of lung cancer is more prevalent amongst the uranium miners who are exposed to radon (radioactive gaseous decay product from uranium and thorium series) and its decay products. The risk of incidence of lung cancer varies with the different smoking habits. Studies have indicated that there is enhancement (synergistic effect) in the lung cancer risk due to radon exposure and the smoking habits of the exposed persons.

This means risk of lung cancer resulting from unit radiation dose due to exposure to radon for people who are smokers is substantially higher than that of people who never smoked.

Exposure to radon is much more injurious to heath if you are a smoker. 

LNT approach is not justified for radiation protection

LNT controversy is appearing again and again in the scientific forums worldwide. In every forum it is said that there is no concrete evidence and justification to accept LNT approach for radiation protection purposes. Finally, it is said that in-spite of all the controversies, LNT is accepted in the radiation protection system since it is easier to manage the radiation doses, and for decision taking regarding w.r.t a practice or procedure.

Why this is forced acceptance? And what cost? Billions of dollars?

As a well-informed radiation protection professional, I am strongly of the opinion that:

1.     ICRP has recommended one-year dose limit of 50 mSv for occupational workers in the System of Dose Limitation. It is assumed that there are no clinically observable biological effects up to a dose of 100 mSv.

Accept 50 mSv as the threshold dose for stochastic effect.

2.     As a measure of good work practice, optimise the occupational exposures in a dose band of 10 to 50 mSv/y. Optimization to be carried out only up to a risk level keeping in view of the overall risk in perspective. 

[10 mSv is the annual dose accepted in radon at work places.] 

ALARA / ALARP / ALATA

The aim of radiological protection must be to prevent unnecessary exposures and to keep the exposures below the internationally accepted ICRP dose limits. It is not possible to control the exposures lower than the background radiation dose levels and hence zero or even close to zero exposures to occupational radiation workers is neither possible or justifiable. Due to its acceptance of LNT theory for radiological protection, and use of As Low As Reasonably Achievable (ALARA) approach, ICRP is over-cautious in its recommendation of ALARA. However, over the years, ALARA has become a regulatory requirement!

The recommendation of ALARA is based on the optimization of the protection taking into account the socio-economic considerations and should remain as the best possible level of protection under the prevailing circumstances. This statement makes ALARA a very uncertain requirement which is difficult to quantify.  

Risk must be averted unless there is gross disproportion between the cost in terms of averting the risk and the benefits of averting such a risk. A proportionate approach - ALARP is the term used in UK legislation, as a requirement that risks to health must be reduced to a level that is As Low As Reasonably Practicable (ALARP). It is the tolerable risk level, which is in- between normally unacceptable and broadly acceptable levels.

 

The “As Low As Technically Achievable (ALATA)” approach is to take the protection level to a level that may be achieved using “World’s Best Practice” utilizing grossly disproportional amount of resources (manpower, money and technology) to reduce exposures which has trivial amount of risk. 

Comment: One sensible and practical approach is to get away from the ALARA, ALARP and ALATA, and ensure that the occupational exposures are strictly maintained below the scientifically derived ICRP dose limits. This will be uniformly in line with the chemical industry where the exposures to chemicals, including carcinogens are regulated by the Threshold Limit Values (TLVs) / Permissible Exposure Limits (PELs). The TLV/PEL of a chemical substance is an exposure level to which a work worker can be exposed for a working lifetime without adverse health effects. The regulation will be through use of SOPs, regular monitoring, periodic review and ensuring compliance. 

2015 Nobel Prize in chemistry for work on DNA repair

Three scientists from Sweden, US and Turkey won the most prestigious Noble Prize for their works on DNA repair mechanism. The three scientists are: Swedish citizen, Prof. Tomas Lindahl (UK); US citizen Prof. Paul Modrich (USA) and US and Turkish citizen, Prof. Aziz Sancar (USA). Prize money of 8 million Swedish Krona to be shared equally between them.

Our body consists of cells of different types. Deoxyribonucleic acid (DNA), stored in the nucleus of every cell, contains genetic code written in chemicals.  DNA replicates itself during cell division. During this process something can go wrong and there can be damage to the DNA molecule. The DNA damage (called mutation) can also take place due to many other reasons, such as exposure to some chemicals, radiation and many other environmental pollutants, both physical and chemical.  The repair mechanism is able to repair this continuous damage of the DNA due to variety of reasons. Prof. Lindahl studied the degeneration or DNA decay over time and how the DNA repair takes place at molecular level.  

Enzymes, viz., specialized protein molecules, act as media in DNA repair through chemical reactions taking place at molecular level. The work carried out by these scientists helped in understanding the working of these repair mechanisms; and will help in better understanding of the chemistry behind ageing process and other diseases, including cancer.

One of the three scientists, Prof. Aziz Sancar worked on repair mechanism of the DNA damage caused by the exposure to visible light and UV radiation. He worked on the repair mechanism which made DNA in bacteria exposed to lethal doses of UV radiation to recover under blue light. However, in mammalian cells, a different repair mechanism, called nucleotide excision repair works. However, there is a possibility of a tiny mismatch during the repair of damaged DNA strands. There exists in the cells, enzymes which repair these mismatches in the DNA strands. Prof. Paul Modrich studied the mechanisms correcting such mismatches.   

My comment: The scientists have been doing great work for years on this all important and complex subject of repair of damaged DNA. The damage has been taking place spontaneously and also due to exposure to other agents, including natural background radiation. I failed to understand how some one can say that the cancer cases seen in the population is due to exposure to low level ionizing radiation from nuclear facilities?  It is time that researchers experimentally prove, beyond doubt, that there is no linear no-threshold (LNT) relationship between exposure to radiation and the cancer.