Answer to Question #7445 Submitted to "Ask the Experts"
Category: Consumer Products
The following question was answered by an expert in the appropriate field:
I've got a question about smoke detectors. I recently found out that the maintenance people in our apartment complex have been cleaning out the insides of old smoke detectors, replacing the batteries, and reinstalling them. I know that smoke detectors have americium inside and I was wondering how easy it would be to dislodge the americium onto the cleaning cloths or onto the outside of the detector. I looked up a site on smoke detectors and found out that, beneath the cap, the americium is not actually encapsulated but is exposed to the air—it sounds like it could be easily wiped off. The maintenance people have seemed careless about other things, and I am concerned that they might not understand the radiation symbol inside the detector and clean vigorously, or even take off the cap covering the americium and upset it.
Since they also clean our apartments, I am worried about the possibility of spreading the substance around when they use those cleaning cloths where it could enter the air and be inhaled; one smoke detector is just 7–10 feet away from my bed. What is the dose we might be exposed to from dislodged americium, by inhalation or skin contact? I don't understand the way they measure radiation dosage; usually they just compare it to an x ray, but an x ray you just get in a split second, and you're not outside in the sun most of the time, so how do you compare these dosages to the constant dosage you might get from being in your apartment about 12 hours a day for a year?
Another concern: We have lots of leaks in our apartment building. What is the possibility of a tiny amount of americium leaching out?
The US Nuclear Regulatory Commission (NRC) regulates the use and distribution of smoke detectors. NRC takes very seriously the concerns that you have regarding the fact that there is the radionuclide americium-241 in smoke detectors. However, before any amount of radioactivity was authorized in smoke detectors, NRC performed several analyses in the 1970s, in 1981, and most recently in 2001 to determine if our earlier calculations regarding any potential health effects from use of such consumer products containing very small amounts of radioactivity would be detrimental before authorizing its use.
NUREG 1717, which is available on NRC's website, discusses the radiological assessment that NRC performed for smoke detectors and other types of consumer products. Radiation doses were estimated for the normal life cycle of a smoke detector, covering routine uses as well as inadvertent uses of the device (such as many thousands of smoke detectors burning in a warehouse fire).
Please be aware that there is a very small amount of 241Am, ~33.3 kBq in a smoke detector. This form of 241Am is embedded (fused) onto a layer of foil and does not pose any danger to you or your family; it cannot be wiped off, nor can it leach off. This is one of the reasons NRC originally authorized its use in the 1970s. In short, the benefits of an operating smoke detector in saving thousands of lives from fire yearly, clearly outweighs the concerns about receiving an extremely small amount of radiation exposure from the use of the device, as described in NRC's environmental assessments (NUREG/CR 1156, NUREG 1717) and the National Council on Radiation Protection and Measurements document NCRP 95. In fact, based on the results of these technical studies and NRC's environmental assessment, the amount of radiation exposure received by an individual who uses a smoke detector is about 80 microSv per year, which is a radiation dose of about 1,000 times less than what you receive from living on planet Earth every day, or 1/3750 of your annual natural environmental radiation dose. (On average we receive about 10 microSv per day from natural background radiation from sources all around us including the sun, the soil, building materials, and your own body.)
NUREG-1717 evaluated several scenarios: (1) a residential fire involving two smoke detectors, (2) a transportation fire involving a typical shipment of 7,200 smoke detectors, and (3) a manufacturer's warehouse fire involving 36,000 smoke detectors (which was also used to assess the potential health effects if these devices were used as a radioactive dispersal device). Even in the latter case, for a firefighter wearing a respirator at this warehouse fire, the individual dose from 36,000 smoke detectors was estimated to be about 3 microGray (still a fraction of what we receive daily from natural background radiation). Remember we each receive about 10 microSv per day of natural environmental background radiation, an extremely low amount relative to the natural environmental radiation around us.
Cynthia Jones, PhD
Slightly reworded and converted to SI units by Orhan Suleiman December 2016.