1000 Backscatter X-ray scanner was developed in 1992 by Dr. Steve Smith. The scanner has been studied extensively for almost 20 years by the leading independent radiation safety authorities in the United States. Experimental and epidemiological data do not support the proposition, however, that there is a threshold dose of radiation below which there is no increased risk of cancer. The UK Health Protection Agency has completed an analysis of the X-ray dose from backscatter scanners and has written that the dose is extremely low and "about the same as people receive from background radiation in an hour". The Health Physics Society (HPS) reports that a person undergoing a backscatter scan receives approximately 0.05 μSv (0.005 mrem) of radiation; American Science and Engineering Inc. reports 0.09 μSv (0.009 mrem). At the high altitudes typical of commercial flights, naturally occurring cosmic radiation is considerably higher than at ground level. The radiation dose for a six-hour flight is 20 μSv (2 mrem) – 200 to 400 times larger than a backscatter scan. The Nuclear Regulatory Commission limits radiation exposure to the public to less than 1 mSv (100 mrem) per year from nuclear power plants. While this is not specifically for airline-associated radiation, the limit is an effective proxy for understanding what level is deemed safe by a regulatory agency. According to a draft standard on the United States FDA website, the allowable dose from a scan would be 0.1 μSv, and that report uses a model whereby a 0.01 μSv dose increases an individual's risk of death by cancer during his or her lifetime by . Since the dose limit is ten times higher than 0.01 μSv, their model would predict one additional cancer death per 200 million scans. Since the airports in the UK handled 218 million passengers in 2009, if all passengers in the UK were scanned at the maximum dosage, then each year this would produce on average one additional cancer death (since there would be 200 million scans per year that the scanners were in operation), though usually each death would not occur in the same year as the particular scan that caused it, since the cancer may take years to grow. In addition, additional people would be given cancer but would die from other causes. There may not yet be evidence of hereditary effects of x-rays administered by backscatter scanners, but backscatter scanners use the same