On thorium and Lynas

On thorium and Lynas

There are 24 comments on the Lim Kit Siang story from Mar 27, 2012, titled On thorium and Lynas. In it, Lim Kit Siang reports that:

MARCH 27 - The Sun declined to publish my response to Dr Looi Hoong Wah's earlier letter .

Join the discussion below, or Read more at Lim Kit Siang.

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Dato Dr Looi Hoong Wah


#29 Jun 9, 2012

"Thorium-232 is strongly bound (adsorbed) by soil especially clay soil. The Thorium concentration in the clay particles is about 500,000 % higher than in the water between the clay particles.

So, it cannot be leached out by water and pollute the rivers. Even if the clay soil is washed into the rivers and sea it will not do any harm as the thorium will still be strongly attached (adsorbed) to the clay and will not dissolve into the water."

Quote Anti-Lynas:
"Lynas' snake-oil salesman forgot to tell you that the WLP waste will be roasted in concentrated acid. And in that form, thorium is highly soluble. Unquote

The SOLUBILITY of a substance in a solute like water and ADSORPTION of the substance are 2 separate properties and not the same.

In nature Thorium-232 is found in the form of Monazite (Ce,La,Nd,Th)PO4 i.e. the phosphate of Thorium-232. This is completely insoluble in water.

The next most common ore is Thorite (ThSiO4) which has a gram molecular weight of 324.12 gm. This is also completely insoluble in water.

Practically most of the other thorium compounds are artificially created in the laboratory. The most famous is Thorium dioxide (ThO2) which was used as a radiological contrast media and because it is also insoluble, it is administered intravenously as a colloidal dispersion of thorium-232 dioxide (Thorotrast)

Huge doses of 25cc to 50 cc of a 25%solution of Thorium dioxide (Thorotrast) was injected into the vein or artery in the contrast radiological studies.

The other Thorium salts like the fluorides, chlorides, Iodides, sulfides, selenides, tellurides, nitrides, nitrates, sulphates and other complexes are all artificially synthesized.

All of these have varying degrees of solubility in water. The most soluble will be the nitrates, chlorides and to a lesser degree sulphates. As mentioned above, the oxides, silicates and phosphates are insoluble.

Metallic Thorium-232 is of course totally insoluble in water.


The extremely dangerous herbicide Paraquat is a liquid and is extremely soluble in water. Although it is extremely soluble and dangerous, IT IS NOT LEACHED OUT OF THE SOIL and pollute the rivers because it is STRONGLY ADSORPED BY CLAY SOIL JUST LIKE THORIUM-232.

So Lynas can continue their acid roasting of the ore and with the usual procedures taken, it should not be a problem.

Dato' Dr Looi Hoong Wah.
FAMM, MB., ChB(Manchester), MRCS(England), MRCP(UK), MRCP(London).
Dato Dr Looi Hoong Wah


#30 Jun 23, 2012
What is the "safe" level of radiation?

Public dose limits for exposure from uranium mining or nuclear plants are usually set at 1 mSv per year above background.

The figures below are given by the National Council on Radiation Protection and Measurement (NCRP) and its international counterpart, the International Commission on Radiological Protection (ICRP). Both of these organizations offer recommendations for the maximum permissible dose (MPD) of radiation.

General Public annual MPD by both NCRP and ICRP is 1 mSv.

For Radiation Workers, the annual MPD is 50 mSv (NCRP) and 20 mSv (ICRP), with a cumulative MPD of 10 mSv x Age.

MPD during pregnancy is 5 mSv (NCRP) and 2 mSv (ICRP).

This is over and above background exposure, and excludes medical exposure.

However, experts including Professor Wade Allison of Oxford University argue that the dose limit can safely be raised to 100 millisieverts, based on current health statistics.

Compare this with the dose of 0.002 millisieverts/year of exposure for people living within 1 km of the Lynas plant in the worst case scenario (estimated by Lynas).

This level of 0.002 mSv/yr is actually grossly overestimated because the low energy gamma rays from the Thorium-232 decay chain is able to travel less than 300 metres in air.

Note, the average energy of most abundant emission is only 0.059 MeV, though the gamma ray from Thallium-208 decay to stable Lead-208 has a higher energy of 2.62 MeV.

The radon-220 has a very short half life of only 55 seconds and as such cannot travel far and do not accumulate in confined spaces like the radon-222 from the Uranium decay series.

So the actual radiation dose at a distance greater than 300 metres from the plant is approaching 0 mSv/year !

Comparative Dosages in Biological Effect in mSv.

Dose from natural radiation in the human body: 0.40 mSv per year

Sleeping next to someone for 8 hours 0.02 mSv/yr (10x Lynas worst case)

Sleeping in wooden house = 0.20 mSv/yr (100x Lynas worst case)

Smoking a pack of cigarettes daily 0.20 mSv/yr (100x Lynas worst case)

Slag brick and granite house = up to 2.0 mSv/yr (1,000x Lynas worst case)

Chest X-ray = 0.10 mSv

Medical or dental X-ray 0.39 mSv

CT Scan (Chest)= 10 mSv

CT Fluoroscopy of abdomen and pelvis 6 to 90 mSv (median=31 mSv)

Average individual background radiation dose: 2 mSv per year (1.5 mSv per

year for Australians and 3.0 mSv per year for Americans)

Dose from atmospheric sources (mostly radon): 2 mSv per year

Total average radiation dose for Americans: 6.2 mSv per year

Current average dose limit for nuclear workers: 20 mSv per year

Dose from background radiation in parts of Iran, India and Europe: 50 mSv per year

(Source: UNSCEAR and EPA and IAEA)

All the potassium that we eat everyday in our food contains potassium-40 and the normal dietary potassium would give a total of about 80 Bq per day.
Compare this with the Lynas waste which produces only 6 Bq/gm

Even your wife or husband is radioactive, with a radioactivity of 4,000 Bq from Potassium-40 and another 3,000 Bq from Carbon-14 giving a total of about 7,000 Bq!

Sleeping next to someone (i.e. your wife or husband) for 8 hours a day will lead to an exposure of 0.02 mSv/year (Source: UNSCEAR and EPA).

Since all living cells contain potassium, all types of meat, flesh, fruits, nuts and vegetables are radioactive because of the potassium-40 content.

The so-called sodium free salt recommended by health experts to combat high blood pressure is nothing more than just highly radioactive potassium salt! Even a lot of doctors, specialists and professors do not know this!

The message here is that more radioactive substances are freely sold in the shops and used as a fertilizer or eaten by us than you would otherwise thought.

Dr Looi

Seri Kembangan, Malaysia

#32 Nov 16, 2012
Dato Dr Looi Hoong Wah wrote:
I have known about the controversy of Thorotrast (a 25 cc vail of a 25% colloidal suspension of Thorium dioxide) since I was a medical student in Manchester about 45 years ago and in fact I have been collecting a fair amount of data with regards to this contrast media.
Thorotrast was given as a contrast media via the vein and the dose of Thorium used was huge, though this depends on the type of radiological procedure done.
It had been estimated that as many as 4 million people were given this contrast in the 1930 to late 1950s.
It has been claimed that there was an increase in the incidence of cancers especially of the liver.
However, we need to consider a number of factors before we can be sure that this is the real culprit.
Are you saying that thorium will not cause cancer ? Or are you saying that YOU DON'T REALLY KNOW, because at the end of the day science is BLIND ?

Seri Kembangan, Malaysia

#33 Nov 16, 2012
Dato Dr Looi Hoong Wah wrote:
The Hon Prof. Chan Chee Khoon:
Quote from the Hon. Professor "...childhood leukaemias observed among the children of Bukit Merah?(Recall also the inverse square law — the intensity of radiation from a radioactive particle a metre away from a human body increases a trillion-fold when that same particle sits at micron-level distances on the body’s cells and tissues.)
Reply by Mr Ng Ai Soo
"The inverse square law applies to trillions and trillions of particles, not just the one particle. That one particle IS the radiation only "dilutes" in a quantum sense... it otherwise remains one particle no matter how far it is from the source... so the cellular damage by that one particle is the same, no matter how far it travelled to get into the cell. But it must survive that journey into the cell and for different particles the survival rates are different.
I think you misunderstood Dr.Chan's contention. He is referring to internal and external emitters. If it is outside then the harm would be less as the energy would have been dissipated over a short distance. But inside the body where the thorium is in close proximity to the cells the damage would be significant.

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