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n 2006, they said that five chemicals — lead, methylmercury, arsenic, PCBs and toluene — should be considered toxic to the developing brain. The doctors did not conduct new studies on these substances, but now, based on a reading of new research, which has been exploding in recent years, they've added six more:• Manganese, a natural chemical found in drinking water in places like Bangladesh.• Fluoride, in high concentrations, which has caused problems in China, though the low levels added to American drinking water are presumed safe.• Chlorpyrifos, an insecticide used on golf courses and in agriculture among other places.• Dichlorodiphenyltrichloroethane (DDT), an insecticide banned in the U.S. in the 1970s, but still used in some countries.• Tetrachloroethylene (PERC), a solvent used in dry cleaning and metal degreasing.• Polybrominated diphenyl ethers (PBDE), also known as flame retardants and often found in furniture, electronics and clothing, including children's pajamas.

38-year-old Toxic Substances Control Act

can the chemicals in the toy result in an exposure, and is this exposure associated with a health risk.  In toxicology, this is described in the following equation: Risk = Exposure x Hazard

hildren under about 3 years of age often mouth toys and other objects.  Mouthing presents a high opportunity for exposure to chemicals, as well as accidental swallowing.  For example, some toy jewelry contains levels of lead and cadmium.  While these toys may be safe if they are only touched (lead and cadmium don’t easily penetrate human skin), they may not be safe if mouthed, since lead and cadmium dissolve in saliva and then get swallowed.

oy Safety Directive 2009/48/EC (TSD)

Most current bactericidal antimicrobials, which are the focus of this review, inhibit DNA synthesis, RNA synthesis, cell wall synthesis, or protein synthesis

Quinolones are derivatives of nalidixic acid, which was discovered as a byproduct of chloroquine (quinine) synthesis

Nalidixic acid and other first generation quinolones (i.e., oxolinic acid) are rarely used today owing to their toxicity17. Second (i.e., ciprofloxacin), third (i.e., levofloxacin) and fourth (i.e., gemifloxacin) generation quinolone antibiotics (Table 1) can be classified based on their chemical structure along with qualitative differences in how these drugs kill bacteria

roject Orion was the first serious attempt to design a nuclear pulse rocket. The design effort was carried out at General Atomics in the late 1950s and early 1960s. The idea of Orion was to react small directional nuclear explosives against a large steel pusher plate attached to the spacecraft with shock absorbers. Efficient directional explosives maximized the momentum transfer, leading to specific impulses in the range of 6,000 seconds, or about 12 times that of the Space Shuttle Main Engine. With refinements, a theoretical maximum of 100,000 seconds (1 MN·s/kg) might be possible. Thrusts were in the millions of tons, allowing spacecraft larger than eight million tons to be built with 1958 materials.

The reference design was to be constructed of steel using submarine-style construction, with a crew of more than 200 and a vehicle takeoff weight of several thousand tons. This low-tech single-stage reference design would reach Mars and back in four weeks from the Earth’s surface (compared to ≈50 weeks for NASA’s current chemically powered reference mission). The same craft could visit Saturn’s moons in a seven-month mission (compared to chemically powered missions of about nine years).

A number of engineering problems were found, and solved, over the course of the project. Many of these related to crew shielding and pusher-plate lifetime. The system appeared to be entirely workable, and was under serious development in the United States, when the project was shut down in 1965. The primary reason given was that the Partial Test Ban Treaty made it illegal to detonate nuclear explosions in space (before the treaty, the United States and the Soviet Union had already detonated at least nine nuclear bombs, including thermonuclear bombs, in space; i.e., at altitudes over 100 km).

chemically modify the antibiotic,  render it inactive through physical removal from the cell, or modify target site so that it is not recognized by the antibiotic.

Efflux pumps are high-affinity reverse transport systems located in the membrane that transport the antibiotic out of the cell.

A specific enzyme modifies the antibiotic in a way that it loses its activity. In the case of streptomycin, the antibiotic is chemically modified so that it will no longer bind to the ribosome to block protein synthesis.

The human health effects of phthalates are not yet fully known but are being studied by several government agencies, including the Food and Drug Administration, the National Institute of Environmental Health Sciences, and the National Toxicology Program's Center for the Evaluation of Risks to Human Reproduction. 

Di(2-ethylhexyl) phthalate is listed as "reasonably anticipated to be a human carcinogen" in the Twelfth Report on Carcinogens published by the National Toxicology Program. 

methylation -- a process by which enzymes add a small molecular tag to a particular location on a nucleotide -- a molecule that is the structural unit of RNA and DNA

facilitates the proper functioning of the bacterial ribosome -- a gigantic macromolecular machine that is responsible for making proteins that bacteria need to survive

antibiotics bind to the ribosome, disrupting its function and thereby killing the bacteria

looks

Bioglass® is a clear bioactive material made of calcium, phosphorous, silicon, and sodium salts. It is a type of artificially made glass classified as a bioceramic. It chemically reacts with body fluids to form a bond at the surfaces of tissues and bones. The elements that make up Bioglass® are needed to repair and grow tissues and bones.

There is no risk of disease or rejection since Bioglass® is made completely of elements found in the human body.

Nuclear fusion rockets could slash travel times through deep space dramatically, potentially opening up vast swathes of the solar system to human exploration

You could get to Saturn in a couple of months

Traditional chemical propulsion systems can get humans to destinations in deep space, but with a lot of travel time. For example, a roundtrip manned mission to the vicinity of Mars, which NASA aims to execute by the mid-2030s, would require about 500 days of spaceflight.

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toxic levels of lead, cadmium, antimony and phthalates, said this year's "Trouble in Toyland" report from the U.S. Public Interest Research Group (PIRG).

f antimony, a toxic metal that has been classified as a cancer-causing agent.

Phthalates are chemicals suspected to cause developmental health effects. Cadmium is a toxic metal that can cause learning disabilities and kidney problems.

The adult human brain is estimated to contain from 1014 to 5 × 1014 (100–500 trillion) synapses. Every cubic millimeter of cerebral cortex contains roughly a billion of them.

searching for a less toxic chemical to use as a new refrigerant.

Antimony compounds are used to make flame-proofing materials, paints, ceramic enamels, glass and pottery

Human exposure to antimony can take place

by skin contact

Humans normally absorb cadmium into the body either by ingestion or inhalation Dermal exposure (uptake through the skin) is generally not regarded to be of significance

2% to 6% of the cadmium ingested is actually taken up into the body. Factors influencing cadmium absorption are the form in which cadmium is present in the food, and the iron status of the exposed individual. In contrast, from 30% to 64% of inhaled cadmium is absorbed by the body, with some variation as a function of chemical form, solubility and particle size of the material inhaled.

a greater proportion of inhaled cadmium is retained by the body than when cadmium is taken in by ingestion.

They're large molecules called polymers, which are composed of repeating units of shorter carbon-containing compounds called monomers

Most plastic is chemically

it doesn't decay. Therefore, plastic disposal poses a difficult and significant environmental problem

hthalates are a group of chemicals used to make plastics more flexible and harder to break.

Once phthalates enter a person's body, they are converted into breakdown products (metabolites) that pass out quickly in urine.