Coal ash contains low concentrations of arsenic, mercury and other heavy metals, although it's not classified as hazardous.
That is dubious: a lack of data makes it much harder to know the effects of such low concentrations.
The scientists said the device could work like "an artificial nose for a robot dog", sniffing out extremely low concentrations of vapour.
He suggested that, even at relatively low concentrations, the compound might possess a "unique capacity" to induce genes which start the bone-building process.
But a cow that lives there and drinks water with low concentrations of iodine will eventually accumulate and concentrate these materials and become unsafe for consumption.
It is unlikely that weak oestrogens such as 4-nonylphenol, which are found in very low concentrations in the environment, play a major role in breast cancer incidence.
They found some evidence that low concentrations of dopamine, a brain chemical, may respond to the sight and smell of food in an addictive manner for some obese people.
Pesticides and other chemicals that could mimic estrogen and disrupt the normal development of salmon are present in the Columbia's water, Nagler said, but at very low concentrations - far below those used in laboratory experiments.
What does that mean? 30 miles out, it would not be dangerous to come into contact with water with low radioactive iodine concentrations.
Their I-131 concentrations appear at the very low end of the range, but are estimated to be drifting both south and east.
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The valleys pose particular problems, with their legacy of ill-health, low skill levels and low employment activity rates, but there are also concentrations of poverty along the North Wales coastline, in south Pembrokeshire and in parts of Cardiff, Newport and Swansea.
"Even if we use the higher concentrations, the concentrations we measured in 2011, the doses to human consumers are very low, and lower than the naturally occurring radionuclides, " he said.
"These foods were chosen because they contain high concentrations of crucial nutrients, as well as the fact that many of them are low in calories, " the website states.
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