Heavy metal (chemistry)
hideA heavy metal is a member of an ill-defined subset of elements that exhibit metallic properties, which would mainly include the transition metals, some metalloids, lanthanides, and actinides. Many different definitions have been proposed—some based on density, some on atomic number or atomic weight, and some on chemical properties or toxicity. The term heavy metal has been called "meaningless and misleading" in an IUPAC technical report due to the contradictory definitions and its lack of a "coherent scientific basis". There is an alternative term toxic metal, for which no consensus of exact definition exists either. As discussed below, depending on context, heavy metal can include elements lighter than carbon and can exclude some of the heaviest metals. Heavy metals occur naturally in the ecosystem with large variations in concentration. Nowadays anthropogenic sources of heavy metals, i.e. pollution, have been introduced to the ecosystem. Waste derived fuels are especially prone to contain heavy metals so they should be a central concern in a consideration of their use.
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News tagged with heavy metals
Hidden Risks Of Modular Classrooms
Nov 18, 2009 |
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Every school day, more than 5 million students in the United States attend lessons held in modular classrooms. With new carpeting and paint, metal roofs and noisy ventilation systems, they can be a health ...
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Exposures to metals and diesel emissions in air linked to respiratory symptoms in children
9 hours ago |
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Exposure shortly after birth to ambient metals from residential heating oil combustion and particles from diesel emissions are associated with respiratory symptoms in young inner city children, according to a new study by ...
New study links alcohol in pregnancy to child behavior problems
10 hours ago |
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A new study from Perth's Telethon Institute for Child Health Research has found evidence that the amount and timing of alcohol consumption in pregnancy affects child behaviour in different ways.
New hydrogen-storage method discovered
Nov 22, 2009 |
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Scientists at the Carnegie Institution have found for the first time that high pressure can be used to make a unique hydrogen-storage material. The discovery paves the way for an entirely new way to approach ...
Researcher: Faint writing seen on Shroud of Turin (Update)
Other Sciences / Archaeology & Fossils
Nov 20, 2009 |
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(AP) -- A Vatican researcher has rekindled the age-old debate over the Shroud of Turin, saying that faint writing on the linen proves it was the burial cloth of Jesus. Experts say the historian may be reading ...
Older problem drinkers use more alcohol than do their younger counterparts
Nov 20, 2009 |
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Older adults who have alcohol dependence problems drink significantly more than do younger adults who have similar problems, a new study has found.
Scientists identify DNA that regulates antibody production
Nov 20, 2009 |
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(PhysOrg.com) -- When foreign invaders trip the immune system’s alarm, antibodies need to be specially sculpted to attack them head on. New research now shows that gene segments called enhancers control the reshuffling of ...
Don't Blame Tryptophan for Thanksgiving Snooze
Nov 20, 2009 |
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(PhysOrg.com) -- Blame it on the heavy meal, the alcohol, or simply the opportunity afforded by a free afternoon on a traditional holiday. Just don't blame it on the tryptophan, say experts at the University ...
Braking news: Particles from car brakes harm lung cells
Nov 20, 2009 |
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Real-life particles released by car brake pads can harm lung cells in vitro. Researchers writing in BioMed Central's open access journal Particle and Fibre Toxicology found that heavy braking, as in an emergency stop, caused ...
The benefits of stress ... in plants
Nov 19, 2009 |
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Chronic stress in humans has been implicated in heart disease, weight gain, and diabetes, among a host of other health problems. Extreme environments, a source of chronic stress, present a challenge even for the hardiest ...
Liquid battery big enough for the electric grid?
Nov 19, 2009 |
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(PhysOrg.com) -- There's one major drawback to most proposed renewable-energy sources: their variability. The sun doesn't shine at night, the wind doesn’t always blow, and tides, waves and currents fluctuate. ...
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