natural background level造句

• Even natural background levels of ozone exceed the legal limit.
• He called the new ozone limit " virtually unattainable " because of the natural background level of ozone.
• Contaminant levels in samples are compared to applicable guidelines and natural background levels to confirm the public is safe and that no health impacts are expected.
• Four decades later, many radioisotopes would have decayed to natural background levels, but long-lived isotopes such as uranium and thorium, which were among the material dumped off Massachusetts, remain radioactive for centuries.
• B . J . Lipari, the company's president, said radiation exposure was lower at Oak Ridge than in the company's old location, in Golden, Colo ., where natural background levels are higher.
• In genetics, a "'mutagen "'is a physical or chemical agent that changes the genetic material, usually DNA, of an organism and thus increases the frequency of mutations above the natural background level.
• Since most emergency workers and people living in contaminated areas received relatively low radiation doses, comparable to natural background levels, no decrease in fertility or increase in congenital malformations have been observed.
• Local environmental groups have voiced concerns about the radioactivity levels of the cooling water of both these nuclear sites, which is being flushed into the bay of Vauville; however, the emitted radioactivity is several orders of magnitude below natural background levels and does not pose any hazard.
• When the doses are very low, at natural background levels, in the absence of evidence, the model predicts via extrapolation, new cancers only in a very small fraction of the population, but for a large population, the number of lives is extrapolated into hundreds or thousands, and this can sway public policy.
• Its recommendation states that " the Scientific Committee does not recommend multiplying very low doses by large numbers of individuals to estimate numbers of radiation-induced health effects within a population exposed to incremental doses at levels equivalent to or lower than natural background levels . " This is a reversal from previous recommendations by the same organization.
• However, a December 2012 UNSCEAR statement to the Fukushima Ministerial Conference on Nuclear Safety advised that because of the great uncertainties in risk estimates at very low doses, UNSCEAR does not recommend multiplying very low doses by large numbers of individuals to estimate numbers of radiation-induced health effects within a population exposed to incremental doses at levels equivalent to or lower than natural background levels ."