Sentences with phrase «chemicals at low concentrations»
«Although these articles concentrate on the US regulatory landscape, they offer an important message that is relevant worldwide: as our understanding of the harmful effects of a combination of chemicals at low concentrations and throughout the human lifespan increases, scientists must re-examine long - held beliefs regarding the relationship between exposure and effect, and ensure that policy makers understand the significance of these findings.»
http://www.sciencemediacentre.org/ Not exact matches
But at pressures found between those two depths, bridgmanite undergoes chemical changes that end up significantly lowering the concentration of iron it contains.
Nor did the EPA show the best understanding of toxicology in urging BP in a directive to use dispersants with a «toxicity value less than» a certain cutoff: in toxicology, a chemical that produces harm at low concentrations, say, five parts per million, is more deadly than those that kill at 10 parts per million.
The technique is so accurate and sensitive that he can determine if there is a molecule of any chemical present even at concentrations as low as one part per billion.
Importantly, the method works even for chemical elements present at very low concentrations, some of which are particularly useful for unveiling magma history with unprecedented detail.
Toxic chemicals in the condensate could harm plankton, fish larvae and invertebrate larvae at fairly low concentrations at the sea surface, he says.
please read Z. Jaworowski's (with Segalstad and Ono) many papers on this subject of trapped gases in glaciers, where he discusses the over 20 mechanical and chemical processes that make accurate measurements impossible; even in shallow cores above the point where co2 is supposedly permanently trap in ice cavities in the firn, co2 concentrations are already 20 - 40 % lower than those measured in air at mauna loa.
But pollution also covers hundreds of chemicals which are fine or even beneficial at low levels but which if released in large quantities or in problematic circumstances cause «harm» — like phosphorus (grows your veges but also leads to toxic cyanobacterial blooms which kill cattle), nitrogen (grows crops kills many native species of plants and promotes weed growth costing farmers), copper (used as an oxygen carrier by gastropods but in high concentrations kills the life in sediments which feed fish), hormones like oestrogen (essential for regulating bodies but in high concentrations confuse reproductive cycles especially with marine life) or maybe molasses from a sugar mill (good for rum but when dumped into east coast estuaries used to cause oxygen sag in estuaries leading to massive fish kills).