What radiation sources am I exposed to?
Radiation exposure/dose per year depends on life choices—however the average, healthy US citizen receives about 360millirem of dose per year.
Airborne/radon, cosmic, terrestrial, and internal/food dose exposures are all due to naturally occurring radioactive materials and sources. 82% of the average US citizen's exposure is from natural sources!
NRCP93 (1987) data. For non-'healthy' individuals who get CT scans or other nuclear medicine diagnostics performed the total dose on average is almost double.
Airborne Radiation: Radon
Radon delivers over half the dose that healthy US citizens receive on an annual basis.
As a colorless gas and a natural product of radioisotopes found in the Earth, radon emanates from the ground and can collect in poorly ventilated indoor or low lying areas. In these poorly maintained environments, radon can pose a health risk. Zone 1 on the map above finds the geological and life style factors that would be most susceptible to radon build up, however radon is naturally found in the air at varying concentrations.
Cosmic rays are another form of naturally occurring radiation that is generated in the upper atmosphere.
High energy particle collisions produce particle cascades that have increasing intensity with higher altitude in the biosphere. Plane flights, for example, increase the amount of cosmic ray exposure a person receives because of the higher cosmic ray intensity.
The Earth’s crust contains several naturally occurring primordial radioisotopes.
These radioisotopes include 238U, 232Th and 40K. These contribute to our natural exposure through the upper 20-80cm of the earth’s surface.
Radiation in the Body: Food
Radioactive materials can be found in our food chain.
Naturally occurring radioactive materials have the same chemistry as their stable analogues. As such, naturally occurring radioactive materials are part of our environment and are found in many elements of our food chains.
Fish from a local Berkeley market. This is part of our "Current Sampling".
Nuclear Medicine and Medical Procedures
Medical imaging and nuclear medicine are widely used for diagnostics and treatments.
These methods typically rely on x-rays or nuclear radiation physics to generate 2&3D images of biological systems.
Medical CT imaging contributes a large fraction of the total average dose to humans. (If one includes this factor the total average dose a person receives is almost doubled.)
Medical CT and angiograms are both sources of dose to individuals getting medical treatments. Over the last 20yrs CT has become very popular and now accounts for half the average dose to US citizens.
RadWatch Project: What We Test
The RadWatch team takes air, food, and water samples to measure and study radiation in our environment.
These samples correspond to the transport methods that radioisotopes from Fukushima could reach the West Coast. Food and water samples are from the immediate Bay Area. Our sister project KelpWatch samples Kelp from the majority of the California coast. Air sampling is performed by the RadWatch Air Monitor. This is a system that can identify radioisotopes in the air. There are no longer any definitive signs of Fukushima in these measurements. Testing these samples provides a band of variance that natural radiation falls into and can serve as a database for radionuclides in the environment.
RadWatch Case Study: Half Moon Bay
Community concerns led researchers to test the beach at Half Moon Bay, investigating possible contamination from Fukushima radiation.
RadWatch team member Ryan Pavlovsky explains that this plot on Google Earth shows the approximate Geiger count rate on the beach approach. Misidentified as Fukushima radiation, the count rate increase is simply due to naturally occurring radioactive materials in the beach geology. This demonstrates the band of variation seen in the natural, radioactive world.