Nuclear Accidents and Food Contamination

[Oscar]

Nuclear Accidents and Food Contamination Part II: Radionuclides and Health Effects

http://elements.healthspace.com/?p=540

January 12, 2009 By: Rosemary Stephen.

(NOTE: Part I is at: http://elements.healthspace.com/?p=255)

In Part I, published in Elements on Nov 20th, 2008, I discussed contaminated wild mushrooms harvested in the nuclear exclusion zones in Europe, and what travelers could do to avoid ingesting caesium-137. Now, in Part II, I will look more closely at what radioactive contaminants may affect our food following a non-occupational nuclear event, what adverse health effects can be expected from these contaminants and what types of treatments are available.

Radiation is measured by a variety of different units, each representing a specific type of radiation exposure. The simplest definition I could find is from Radiation Emergencies from the US CDC; it states that the amount of radiation being given off, or emitted, by a radioactive material is measured using the conventional unit curie (Ci), named for the famed scientist Marie Curie, or the SI (International System) unit becquerel (Bq). The radiation dose absorbed by a person (that is, the amount of energy deposited in human tissue by radiation) is measured using the conventional unit rad or the SI unit gray (Gy). The biological risk of exposure to radiation is measured using the conventional unit rem or the SI unit sievert (Sv)[1].

When cells are damaged by radiation, particles called free radicals are created which may interfere with cellular replication, structure and function [2]. Some body tissues are more susceptible to damage from radiation than others and some types of radionuclides target specific organs. Some radionuclides (like Iodine-131) are chemically identical to substances the body needs in order to function so it cannot discriminate between radioactive and non-radioactive forms and may concentrate the radionuclide in particular tissues (such as the thyroid gland).

What are radionuclides? They are species of radioactive atoms, whether man-made or from natural sources. All elements have radioactive forms and most elements have many such forms, so there are many hundred known species of radionuclide. For example: 98.9% of naturally occurring carbon is carbon-12, with 6 neutrons and 6 protons in each nucleus; 1.1% is carbon-13 and has an extra proton in each nucleus; both these nuclides are stable and therefore not radioactive. Carbon-14, however, is unstable with half of its atoms decaying in 5730 years (on average), its nuclear half-life, by emitting a beta particle (an energetic electron in this case); it is therefore a radionuclide of carbon. Some elements, such as Plutonium, have no stable forms.

Studies done after Chernobyl have identified five radionuclides out of the 60 emitted by the disaster as being responsible for serious, adverse health effects in humans, animals and plants. These are: Iodine-131, Caesium-137, Strontium-89 and 90, and Plutonium. Let's have a look at each one.

Iodine-131 is a volatile, gaseous, radionuclide that emits beta particles and gamma rays. It combines easily with organic materials and some soil minerals. Water, grass, leafy vegetables and animal forage become contaminated with iodine during fall-out. The nuclear half-life of iodine-131 is 8 days, but once ingested, the level of cell damage depends on how quickly it is eliminated from the various tissues in the body. In the kidney, spleen, and reproductive organs half the iodine will be eliminated in 7 days (its biological half-life causing cellular damage [3]. In bone marrow, however, it persists with a biological half-life of 14 days and can cause leukaemia [4]; in the thyroid it has a biological half-life of 100 days - long enough for almost all of it to decay - perhaps causing either malignant or benign tumors. Children and young adults less than 20 years of age are highly vulnerable.

Potassium iodine supplements are given to prevent the retention of iodine-131 in the body. It is an inorganic compound that looks like salt. Once ingested, potassium iodine saturates the body with a source of stable iodine-127 promoting the excretion of iodine-131. It is given orally once a day for a period of 10 days and the exact dosage varies depending upon the age of the patient. Usually 130mg is given to adults and teenagers while 65mg is given to children [5].

Caesium-137 (Cesium-137) emits beta particles and strong gamma rays. Caesium moves easily in the environment making it impossible to clean up. People are exposed simply by walking outside on contaminated soil, breathing dust or drinking from surface water sources. When ingested, caesium is absorbed by the intestinal tract and thereby into the body [6]. When inhaled, caesium-137 will move throughout the body and settle in slightly higher concentrations in muscle tissue and in slightly lower concentrations in bones and fat, eventually causing cancer. The human body eliminates some caesium naturally in urine but some is also retained in bodily tissues; in adults approximately half of the caesium load is eliminated in 110 days, in children, however, the elimination rate is slightly slower with approximately half of the caesium eliminated after 119 days [7]. Caesium-137 has a nuclear half-life of 30 years. It is toxic to the whole body especially if exposure levels are at or above 50 Becquerel per kilograms of body weight, eventually causing irreversible lesions throughout the body [8].

Naturally, a diet free of contaminated food will reduce the caesium-137 burden, but it is also vital that people who have been exposed be given agents that will prevent the absorption of caesium into the body. Suggested agents include Prussian blue and apple pectin. Numerous studies are being done to test the ability of these two agents to trap caesium in the intestine where it will be eliminated naturally along with excrement.

Prussian blue has been used since the 1960’s to trap caesium-137 and other agents, such as heavy metals. Given under a doctor's supervision for one month, it is said to reduce the biological half-life of cesium from about 110 days to about 30 days helping limit the amount of time the body is exposed to radiation[9]. The drug is safe for most adults including pregnant women, and children (2 ─12 years). Dosing for infants (ages 0 ─2 years) has not been determined yet. Prussian blue is only available by prescription.

A German-Belarusian project tested apple pectin in a population of 729 children whose body burden of caesium-137 was in excess of the international annual dose of 1 mSv. All children were given non-contaminated foods, additionally half received Vitapect and the other half a placebo. The results of the pectin test group indicated a decrease in caesium-137 body burden of 33% against the placebo group with only a 14.2% decrease. The Vitapect also influenced the speed the body eliminated caesium-137, resulting in an achieved biological half-life of 69 days for the placebo group and only 27 days for the Vitapect group. This simple supplement is made from apple pectin mixed with vitamins, minerals and flavouring agents. It is regulated and licensed by Belarusian authorities and is given to children in an oral dosage of 5g BID for two weeks. Vitapect as the advantages of being affordable and easily available [10].

Strontium-89 is a pure beta emitter with a half -life of 50 days. It is not as significant as Strontium-90 which has a half life of about 29 years. The presence of Sr 90 in the environment has decreased since nuclear weapon testing has (mostly) stopped. Now it is found after nuclear accidents and in zones around nuclear power plants. Both strontium-89 and 90 are present in dust, in food and water. Once ingested, 20% to 30% will remain in the body and is subsequently deposited in bones (including teeth). Because it follows the calcium cycle, bone cancer, cancer of the soft tissue or leukemia will develop in time [11].

Seaweed may be helpful in ridding the body of strontium-89 and 90. The first studies on the viability of seaweed to combat radiation poisoning were started 30 years ago at McGill University in Montreal, Canada. It was discovered that alginates found in large brown algae like Kelp and Alaria have the potential of reducing the amount of strontium-90 absorbed through the intestinal wall. The American EPA's Environmental Toxicology Lab in Oak Ridge Tennessee have also found that alginates could bind and eliminate strontium-90 from the body and even from bones [12]. A more recent study done on sodium alginates shows that it too is potent in reducing strontium absorption and without any toxicity [13].

Plutonium-239 is a long lived alpha emitter with no penetrating power, but once in the environment, it becomes more biologically available as it ages. Plutonium-239 can be ingested by mouth or inhaled. Some plutonium-239 is expelled naturally via feces (ingested plutonium) or in phlegm (inhaled plutonium), but much remains in the body. These non-excreted particles will eventually enter the bloodstream and move into bones, the liver and other organs. Plutonium-239 will then irradiate these organs for decades and eventually cause cancer [14]. Chelation therapy, drugs that increase the solubility of plutonium and the body's ability to eliminate it with urine, are recommended for the treatment of plutonium inhalation [15]. Plutonium is not easily absorbed by the intestinal walls so most of it will be excreted [16].

A full study of all the radionuclides that affect human health is not possible in this article, I have instead looked at the most common and the most destructive to human health. There are some treatments available to people who have been exposed to radionuclides, but we, as inspectors, must also ensure that any ingestion of local, likely contaminated food, is stopped immediately after a nuclear event. These same precautions apply to the ingestion of milk from cows that ate contaminated forage and to the ingestion of leafy vegetables from private gardens [17]. It is vital that non-contaminated foods from approved sources be made available to adults, and especially to children, for at least one month after an incident. If this is not done, serious medical conditions will appear in the exposed population over time.

Now that we know more about the main types of radionuclides, how do we know which foods are safe to consume and what to recommend? These questions will be discussed in detail in Part III of Nuclear accident and Food Contamination. I hope you will join us.

References:

[1] Fact Sheet, Radiation Measurement (2003) Department of Health and Human Services, CDC Radiation Emergencies. (On-line)
Available: http://www.bt.cdc.gov/radiation/pdf/measurement.pdf.
Cited 2008 Dec 22.

[2] The Chernobyl Nuclear Reactor Accident (2004)(On-line) Available: http://www.uio.no/studier/emner/matnat/ ... M5900/h04/
Innleveringer/Chernobyl_accident-AH_TKF_Sep2004.pdf. Cited 2008 Dec 15.

[3] Radiation protection, Iodine. (2008). US Environmental Protection Agency. (On-line). Available: http://www.epa.gov/rpdweb00/radionuclid ... #wheredoes. Cited 2008 Oct 28

[4] DR. Bertell, R. Cell Damage Expressed as a Health Problem (2008) Part One, The Problem: Nuclear Radiation and its Biological Effects. (On-line)
Available: http://www.ratical.org/radiation/NRBE/N ... fects.html.
Cited 2008 Dec 12.

[5] Iodine and Potassium Iodide (Strong Iodine) (Oral Route), Drug and Supplements. (2007) MayoClinic.com. (On-line)
Available: http://www.mayoclinic.com/health/drug-i ... n/DR600175.
Cited 2008 Dec 12

[6] Shapley, A.J. Contamination of Food Problem After Nuclear War.(1985) Study Prepared for Bruce Beach. (On-line)
Available: http://webpal.org/b_recovery/1_radiatio ... ymain.html Cited 2008 Oct 30.

[7] Rôle de la pectine dans l’élimination du césium dans l’organisme (2004) Résultats d’analyses sur des enfants biélorusses, ACROnique du nucléaire n°67. (On-line) Available:
http://www.acro.eu.org/pectine.html. Cited 2008 Dec 12.

[8] Radiation protection, Cesium. (2008). US Environmental Protection Agency. (On-line). Available: http://www.epa.gov/rpdweb00/radionuclid ... #wheredoes. Cited 2008 Oct 28

[9] Prussian Blue, Fact Sheet (2006) Emergency ¨Preparedness and Response, Centers for Disease Control and prevention. (On-line) Available: http://www.bt.cdc.gov/radiation/prussianblue.asp. Cited 2008 Dec 22.

[10] P. Hill and al. (2006) On the reduction of internal radiation doses resulting from ingestion of Cs-137 in areas contaminated by the Chernobyl accident, Session TA8 - Incidents and Accidents. (On-line) Available: http://www.science-connections.com/book ... paper3.pdf. Cited 2008 Dec 15.

[11] Radiation protection, Strontium. (2008). US Environmental Protection Agency. (On-line). Available: http://www.epa.gov/rpdweb00/radionuclid ... #wheredoes. Cited 2008 Oct 29.

[12] Sea Vegetables and Radioactive/Heavy Metal Detoxification.(2000) Sea Vegetation. (On-line) Available: http://www.envirohealthtech.com/sea_vegetation.html. Cited 2008 Dec 23.

[13] Strontium Biokenetics in Humans: Influence of alginate on the Uptake of Ingested Strontium.(2004) The radiation Safety Journal, Health Physics Society. (On-line) Available:
http://www.health-physics.com/pt/re/hea ... 00011.htm;
jsessionid=JR0VRRfTpLyfGhnvHJXT2N12gJgVBQ9q
K1BT3Q02hwrydJ9s0dlH!-2112048807!181195629!8091!-1.
Cited 2008 Dec 23.

[14] Radiation protection, Strontium. (2008). US Environmental Protection Agency. (On-line). Available: http://www.epa.gov/rpdweb00/radionuclid ... #wheredoes. Cited 2008 Oct 29.

[15] Modes of Exposure and Treatment, Medical Treatment, Chelation Therapy (2008) Instructor’s Guide, Radiological Safety Training for Plutonium Facilities, DOE–HDBK–1145–2008. (On-line) Available: http://hss.energy.gov/NuclearSafety/tec ... /hdbk1145/
DOE-HDBK-1145-2008_0808.pdf. Cited 2008 Dec 23.

[16] Makhijani, Arjun. Health Effects of Plutonium (1997) IEER, Energy and Security No.3. (On-line) Available: http://www.ieer.org/ensec/no-3/puhealth.html. Cited 2008 Dec 12.

[17] Staff Report, International Atomic Energy Agency (2005)
IAEA.org. (On-line)
Available: http://www.iaea.org/NewsCenter/Features/
Chernobyl-15/thyroid.shtml. Cited 2008 Oct 28.
.

Rosemary Stephen (2009). Nuclear Accidents and Food Contamination Part II : Radionuclides and Health Effects Elements