Alpha emitters are radioactive elements that emit alpha particles as they undergo radioactive decay. Alpha particles are composed of two protons and two neutrons, making them essentially the same as a helium-4 nucleus. Due to their relatively large mass, alpha particles are the least penetrating type of radiation and can be blocked by materials as thin as a sheet of paper. However, if alpha-emitting materials are inhaled or ingested, they pose serious health risks due to the dense ionization caused along their tracks within tissue. In this article, we will explore what alpha emitters are, their sources and applications, as well as associated health hazards and safety precautions.

Natural Sources of Alpha Emitters

Naturally occurring alpha emitters are found in trace amounts within minerals and ores throughout the earth's crust. Uranium and thorium are two of the most abundant alpha-emitting radionuclides present in nature. Uranium-238 and thorium-232 have half-lives of over 4 billion years and can be found in uranium-containing ores and deposits around the world. Due to their long half-lives, uranium and thorium have existed in the crust since the formation of the planet. Other common natural alpha emitters include radium-226, which is part of the uranium-238 decay chain, and polonium-210 in the thorium-232 chain. Low levels of radon gas, composed of radon-222 decaying from radium-226, can be found emanating from soils worldwide.

Man-made Alpha Emitters

In addition to naturally occurring alpha emitters, a number of man-made radionuclides that emit alpha particles have been produced. The transuranic elements like plutonium-238, -239, -240, -241, -242 and americium-241 are commonly generated as byproducts of nuclear fission reactions in reactors. These heavy actinide elements have high density and decay by predominantly emitting alpha particles. Plutonium-238 in particular has found applications as a power source for remote devices due to its thermal energy output. Another produced alpha emitter is radium-226, which can be separated from uranium enrichment waste. Historical uses of radium included luminous paint for watches, compasses, and dials.

Health Hazards of Alpha Emitters

The primary health hazard from Alpha Emitters comes from internal exposure through inhalation, ingestion, or absorption. Due to their high energy and mass, alpha particles deposit all of their kinetic energy along a very short track within exposed tissue. This results in dense ionization that can severely damage DNA and critical cellular structures if exposure occurs internally. When alpha emitters are inside the body, they have been linked to increased cancer risks, especially lung cancer if inhaled or ingested. Even small quantities of plutonium, polonium or radium isotope incorporated in the body significantly boost the lifetime risk of developing cancer. Additionally, repeated exposure to alpha emitters over long periods can lead to non-cancer diseases like radiodermatitis. For these reasons, great care must be taken to avoid internal contamination from alpha particle-emitting radioactive materials.

Safety Precautions

Given the severe biological impacts posed by internal alpha emitter exposures, strict safety precautions are required when working with these radioactive isotopes. Sources must be properly handled, contained and stored using shielding to prevent the emission or spread of any alpha particles. Personal protective equipment like respiratory masks, gloves, lab coats and special HEPA filters are required depending on the activity of materials. Monitoring stations and surveys are conducted regularly to confirm containment. In the event of accidental releases, rapid response plans aim to isolate, decontaminate and monitor impacted areas or individuals. Proper handling and disposal procedures are crucial to avoid exposures to workers, the public or the environment. Furthermore, constant radiation monitoring and comprehensive worker protection programs are enforced wherever alpha emitters are utilized or produced.

Alpha emitters are a class of radioactive elements that undergo decay through emission of alpha particles. Naturally occurring alpha emitters like uranium, thorium, radium and radon are present in low amounts in soils and minerals. However, a number of other alpha nuclides have been artificially produced. While alpha particles themselves pose little external hazard, the health risks from internal exposures through inhalation or ingestion of alpha emitters are extremely severe due to dense ionizing radiation deposited along intracellular tracks. Strict regulations, containment controls, personal protective measures and radiation safety practices have thus been established wherever alpha emitters are present to minimize exposure risks to workers, public health and the environment. 

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