Thursday, August 28, 2014
A century ago, miners working in California's Death Valley reported seeing boulders on the desert floor with long trails behind them — as if the stones had been pushed across the sand. But despite 60 years of trying, no one ever saw what moved them.
Wednesday, August 27, 2014
Tuesday, August 26, 2014
Saturday, August 23, 2014
Friday, August 22, 2014
Thursday, August 21, 2014
Thursday, August 14, 2014
Saturday, August 9, 2014
Wednesday, August 6, 2014
Friday, August 1, 2014
How does radioactive material get into a cigarette?
The tobacco leaves used in making cigarettes contain radioactive material, particularly lead-210 and polonium-210. The radionuclide content of tobacco leaves depends heavily on soil conditions and fertilizer use.
Soils that contain elevated radium lead to high radon gas emanations rising into the growing tobacco crop. Radon rapidly decays into a series of solid, highly radioactive metals (radon decay products). These metals cling to dust particles which in turn are collected by the sticky tobacco leaves. The sticky compound that seeps from the trichomes is not water soluble, so the particles do not wash off in the rain. There they stay, through curing process, cutting, and manufacture into cigarettes.Lead-210 and Polonium-210 can be absorbed into tobacco leaves directly from the soil. But more importantly, fine, sticky hairs (called trichomes) on both sides of tobacco leaves grab airborne radioactive particles.For example, phosphate fertilizers, favored by the tobacco industry, contain radium and its decay products (including lead-210 and polonium-210). When phosphate fertilizer is spread on tobacco fields year after year, the concentration of lead-210 and polonium-210 in the soil rises.
What happens when I smoke a cigarette?
Research indicates that lead-210 and polonium-210 are present in tobacco smoke as it passes into the lung. The concentration of lead-210 and polonium-210 in tobacco leaf is relatively low, however, this low concentration can accumulate into very high concentrations in the lungs of smokers.
As it passes into the lungs, the smoke impacts the branches of the lung passages, called bronchioles, where the branches split. Tar from tobacco smoke builds up there, and traps lead-210 and polonium-210 against the sensitive tissues of the bronchioles. Studies show filters on ordinary commercial cigarette remove only a modest amount of radioactivity from the smoke inhaled into the lungs of smokers. Most of what is deposited is lead-210, but polonium-210 (whose half life is about 138 days) quickly grows in as the lead-210 (half life = 22.3 years) decays and becomes the dominant radionuclide. Over time, the concentration of polonium-210 directly on tissues of the bronchioles grows very high, and intense localized radiation doses can occur at the bronchioles. epa.gov
_______________________________________Review Article: Polonium and Lung Cancer by Vincenzo Zaga, Charilaos Lygidakis, Kamal Chaouachi, and Enrico Gattavecchia
In the Journal of Oncology, 2011
Polonium is a highly toxic element, with elevated specific radioactivity, and is dangerous to handle even in milligram amounts. The maximum allowable body burden for ingested Polonium is 1100 Bq, which is equivalent to a particle weighing only 6. 6 Å~ 10−6 μ g . Alpha rays, which are formed by helium 4 (He-4) nucleus, are the least penetrating type of radiation and they manage to travel only a few centimeters in air. They can be easily stopped by obstacles, such as a sheet of paper, and they can penetrate living tissues by only a few microns [55, 58, 59]. In fact, since they lose all of their energy after a short distance, they can be dangerous for tissues only when substances emitting alpha particles enter the organism by respiration or ingestion. In addition, alpha rays are highly ionizing and, therefore, are particularly harmful for living tissues. 1 mg of polonium can emit as many alpha particles as 5 grams of radium. The impact on humans can be devastating, as it can cause considerable damage by causing cell death, promoting a massive, progressive, and rapid necrosis, and not allowing the organism enough time to replace the quantity of dead cells .
The journey of Po-210 and Pb-210 towards bronchopulmonary apparatus starts by lighting a cigarette. In this combustion chamber, tobacco burns, reaching 800–900◦ C when inhaling, and smoke is created, which is composed of a corpuscular (5%) and a gas phase (95%) . Po- 210 and Pb-210 are adsorbed in the insoluble particles of the corpuscular phase . The latter is present in a high quantity and is a weak alpha (< 1Å~ 10−5 ), gamma, beta, and X emitter. All these inhaled particles are deposited in the broncho-pulmonary apparatus and particularly in segmental bronchi bifurcations, due to ciliary action. According to measurements by Cohen et al., radium and thorium are also present in cigarettes; however, 99% of the radioactivity comes from Po-210 , which remains in the bronchopulmonary apparatus after inhalation . All these particles have a diff erent “destiny” based on the efficacy of the mucous-ciliary clearance. This mechanical purification is reduced gradually in smokers with COPD, resulting in the accumulation of insoluble Pb-210 particles, which decay to Po-210 over time [70, 77]. In fact, the more severe COPD becomes, the greater the risk of radioactive load accumulation is . Subsequently, radioactive particles reach various organs and tissues through pulmonary and systemic circulation and cause mutations of the genetic cellular structure, deviations of the standard cellular characteristics, accelerated aging, and quicker death due to a wide range of diseases [78, 79]. In smokers, Po-210 levels are in fact significantly higher in blood (by 30%) [65, 80], urine (6-times higher) , liver, kidney, heart, and psoas muscle . Little and McGandy estimated that Po-210 concentration in blood is 63.64mBq/kg of blood in smokers and 28.12mBq/kg of blood in non-smokers . Notably, concentrations of Pb- 210 and Po-210 in rib bones and alveolar lung tissues were two-times higher in ex-smokers compared to non-smokers, even a year after smoking cessation .
DNA chromosome damage by exposure to alpha radiation is 100-times greater than the one caused by other types of radiation . Little and Radford estimated that the radiation dose of the bronchial epithelium of bifurcations in the inferior lobes of people smoking for 25 years would be 2 Sv . This can be explained by the local accumulation of Pb-210 insoluble particles . According to Martell, the cumulative dose of alpha radiation in bronchial bifurcations of smokers that die of lung cancer is approximately 16 Sv (80 rad). This dose is suffi cient to induce a malignant transformation caused by alpha-particles interaction with basal cells [115, 116].
"To render the biological harm deriving from Po-210 in smoke more comprehensible, it has been compared to the damage caused by radiation in conventional chest X-rays. Since the dose of a modern chest radiograph is 0.034mSv [125, 126], a smoker of 20 cigarettes per day receives a radiation dose of 0.08–0.09 Sv equivalent to approximately 300 chest X-rays per year [98, 99, 113, 127]."