Long-term but low-level exposure to cadmium, a metallic element commonly used in batteries and electrical products, may lead to cancer, a study published on Sunday suggests.

Most cancer-causing substances work by directly damaging the DNA of a cell, inflicting changes in the genetic code that causes the cell to proliferate uncontrollably.

Cadmium is a known carcinogenic but the authors say, it seems to work dangerously subtly by targeting a mechanism called mismatch repair, which roots out and fixes mutations that can spontaneously occur in cells after they divide.

If the repair system is inhibited, that allows genetic flaws to be passed on in the cell and its descendants, thus boosting the risk that they will become cancerous.

Inherited glitches in mismatch repair have long been fingered as potential causes for cancer, but the big unknown is whether this mechanism can also be affected by substances in the environment.

Dmitry Gordenin at the US National Institute of Environmental Health Sciences tested several agents to see if they affected mismatch repair in yeast, a closely studied lab subject.

Prolonged exposure to low, non-lethal doses of cadmium increased the level of DNA damage in yeast cells by up to 2,000 times, Gordenin's team reports in Nature Genetics, a specialist monthly journal published by Nature.

"The strong mutagenic action of cadmium was observed at concentrations comparable to those found in the environment and at levels that can accumulate in the human body," they write.

"Further studies are needed to identify conditions and cell types in which cadmium could inhibit human (mismatch repair)," they say. "Even moderate inhibition of (it) has implications for human health."

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New Delhi: While the world is worried about impending water crisis, geophysicists in Switzerland have found the first evidence for water deep inside the Earth's upper mantle.

Mark van der Meijde and colleagues at the Swiss Federal Institute of Technology in Zurich analysed seismic waves from below the Mediterranean sea and believe that parts of the upper mantle could contain as much as 700 parts per million of water by weight.

Mantle is the 400 to 700 km thick region of the Earth that lies below the crust and above the core. According to the report the water found in the upper mantle was released from moving oceanic plates.

The Swiss team analysed seismic waves by structures in the discontinuous regions.

They found that the region at 410 km is much wider than expected, suggesting that the widening - which is 20 to 30 km thick - is caused by the fault mechanisms and predict Earthquakes, they report in the journal Science.

The team plans to look at other tectonic plate boundaries in the world to see if it can find more evidence for water at such depths.

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ONE OF the worst pollution menaces of modern times is packaging plastic, because of its poor degradability. Paper is being pushed as an alternative, but it lacks the strength and convenience of plastic.

A 42 month research project involving several European organisations and coordinated by the Netherlands-based R & D organisation, TNO, has now come up with a new, low-cost biopolymer which combines the strength and flexibility of plastic with the degradability of paper. The biopolymer is derived from two very cheap raw materials - starch and clay.

The general objective of the project was to develop a new biodegradable food packaging material with a low permeability for oxygen, carbon dioxide, nitrogen and water vapour, by homogeneously dispersing functionalised layered silicates (clay minerals) in thermoplastic starch via polymer melt processing techniques.

Native starch is cheap but highly hydrophilic and the quick ageing is a serious problem for most applications. This problem was sought to be overcome by forming a nanocomposite of starch and clay. The obtained starch/clay nanocomposite films show a very strong decrease in hydrophilicity.

The addition of clay during processing supports and intensifies the de-structuring process of starch, providing a means of easier processing (lower extrusion temperature and less processing agents).

The stiffness, the strength and the toughness of the nanocomposite material are improved and can be adjusted by varying the water content.

The term `layered clay' is commonly referred to naturally occurring layered silicates, like for example talc, mica and generally all the group of the smectic minerals. These materials are characterised by a periodic stacking of layers, with a weak interaction between the layers and a strong interaction within the layers.

Homogeneous dispersion of clay in the starch matrix is imparted by a compatibiliser. The compatibilisers investigated were organic aliphatic cations, cationic starch-like materials, maltose-based compatibilisers and water. In this project, layered aluminium silicates were modified using amine-functionalised surfactants.

Another aim of the project was to develop modified starches like starch acetate (SA) with increased hydrophobicity, suitable for making starch-clay nanocomposites by polymer melt processing. One of the project participants, Biopolymer Technologies of Dresden, Germany, has developed a production process for SA that is characterised by the in situ production of the plasticiser - glycerol acetate - during the reaction. Thus the difficulties in mixing pure SA with a plasticiser are avoided.

Samples produced by BIOP in pilot plant scale have proved that a blend made from preformed and dried TPS-clay composite and a relatively small amount of a biodegradable polyester can be processed to blown films in a proper way, if the TPS-clay contains a certain amount of the prepolymer and an antiblock agent.

Water resistant extruded flat films (thickness 0.5 mm) based on thermoplastic starch containing clay nanoparticles can be produced on an industrial scale. TNO's patented method uses extrusion to blend in a single step clay particles into a starch polymer matrix . This process occurs at temperatures higher than 90 degrees C , with the addition of water and plasticisers.

The total content of plasticizer (water + glycerol) necessary for the extrusion lies in the range of 30 to 40 per ecnt, thus giving the mixture a rather sticky texture. Film blowing of pure TPS-clay samples is not possible due to a poor melt toughness (strength of the hot blown film) and the stickiness caused by the necessary high content of plasticiser. Consequently films with a thickness below 100 m are only accessible by film blowing of blends compounded from thermoplastic starch-clay mixture together with a polyester.

A full characterisation of samples obtained in the lab andl as on a commercial scale has been performed to determine the suitability of starch-based nanocomposite films in order to be utilised for food packaging applications. It was assessed that the contact of these films with vegetables does not result in any increase of metal content and thus can be safely used in packaging vegetables.

The biodegradation tests have shown that the nanocomposite films meet the European standards on packaging and packaging waste. Once in the compost heap , this material decomposes within a matter of months and all that is left are the clay particles.

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Bangalore, June 11: Southwest monsoon has advanced into Goa, some more parts of Karnataka and Tamil Nadu and is likely to cover more areas in the two states in the next couple of days, Meteorological Department Officials said on Wednesday.

"Monsoon has entered into Goa and advanced into some more parts of coastal and south interior Karnataka and Tamil Nadu," Director, Indian Meteorological Department, R D Singh said.

Conditions are favourable for further advance of the monsoon into remaining parts of coastal and south interior Karnataka during the next 48 hours, he said.

He said that moderate to heavy rainfall was recorded in Konkan, Goa, coastal Karnataka, sub-Himalayan West Bengal, Northeastern states including Sikkim.

Rains over Konkan and Goa, coastal Karnataka, Northeastern states are likely to continue, he said.

Meanwhile, the northern branch of monsoon has reached Panjim, Nagapattinam, Jalpaiguri and Gangtok, he said.

Significant amounts of rainfall was recorded in Agartala - 08 cm, Gangtok - 05 cm and Karwar - 04 cm, he said adding pre-monsoon showers over Mumbai were also recorded. On the temperature in the capital, he said Delhi recorded a maximum of 42.5 degree celsius. The temperature is likely to reach a maximum of 42 degree celsius.

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