as the health consequences of those things (particularly in the short term) can be more severe than those of tritium exposure. Environmental contamination Tritium has leaked from 48 of 65 nuclear sites in the US. In one case, leaking water contained of tritium per liter, which is 375 times the current EPA limit for drinking water, and 28 times the World Health Organization's recommended limit. This is equivalent to or roughly 0.8 parts per trillion. The US Nuclear Regulatory Commission states that in normal operation in 2003, 56 pressurized water reactors released of tritium (maximum: ; minimum: ; average: ) and 24 boiling water reactors released (maximum: ; minimum: 0 Ci; average: ), in liquid effluents. 40,600 Curie of tritium are approximately equivalent to According to the U.S. Environmental Protection Agency, self-illuminating exit signs improperly disposed in municipal landfills have been recently found to contaminate waterways. Regulatory limits The legal limits for tritium in drinking water vary widely from country to country. Some figures are given below: {| class="wikitable" |+ Tritium drinking water limits by country !valign="bottom"| Country !valign="bottom"| Tritium limit(Bq/L) |- | Australia |align="right"| 76,103 |- | Japan |align="right"| 60,000 |- | Finland |align="right"| 30,000 |- | World Health Organization |align="right"| 10,000 |- | Switzerland |align="right"| 10,000 |- | Russia |align="right"| 7,700 |- | Canada (Ontario) |align="right"| 7,000 |- | United States |align="right"| 740 |- | Norway |align="right"| 100 |- |} The American limit is calculated to yield a dose of 4.0 millirems (or 40 microsieverts in SI units) per year. This is about 1.3% of the natural background radiation (roughly 3,000 μSv). For comparison, the banana equivalent dose (BED) is set at 0.1 μSv, so the statutory limit in the US is set at 400 BED. Use Biological radiometric assays Tritium has been used for biological radiometric assays, in a process akin to radiocarbon dating. For example, in one paper, [3H] retinyl acetate was traced through the body of Sprague-Dawley rats. Self-powered lighting The beta particles emitted by the radioactive decay of small amounts of tritium cause chemicals called phosphors to glow. This radioluminescence is used in self-powered lighting devices called betalights, which are used for night illumination of firearm sights, watches, exit signs, map lights, navigational compasses (such as current-use M-1950 U.S. military compasses), knives and a variety of other devices. , commercial demand for tritium is per year and the cost is or more. Nuclear weapons