® DEMYSTIFYING EVERYDAY CHEMISTRY FEBRUARY 2010 Chemistry in the Operating Room How Anesthetics Make Surgery Pain-Free, p. 8 Turning Plants into Green Gasoline, p. 13 What’s so Special about Mineral Makeup?, p. 16 QUESTION FROM THE CLASSROOM By Bob Becker Reprinted from ChemMatters, December 2004. body weight would have a 50:50 chance of dying. A rat having OTODISC only 13 mg of arsenic injected h What is the most deadly poison in the world? P intraperitoneally would have the Q same risk. If this can be applied to average (75 kg) humans, it would take 57,000 mg (57 g, about 2 oz) of ingested arsenic The answer to your ques- alone, and 4–5 million worldwide. 100% of the population). LD50 A tion depends on how No other poison even comes serves as a sort of average lethal to kill off an average human. As it you define “poison” and what close to these numbers. dose. It is important to point out turns out, compounds of arsenic you mean by “most deadly.” You Tobacco is a chronic poison; that these toxicity tests are not are considerably more lethal than might be tempted to define a poi- repeated exposure to it over the conducted on humans (obvi- the element itself. The ORL-RAT son as being any chemical that long term kills. If one decides ously), but instead on laboratory LD50 for diarsenic pentoxide can cause death, but this is prob- to ignore the actual death toll animals such as rats and rabbits. (As2O5) is only 8 mg/kg—mean- ably not a very good definition. caused by a poison and focus One could certainly question how ing that it would only take 600 It would have to include water, instead on its sheer potency, ethical such research is, or even mg (0.6 g, about half the mass of since drowning accounts for then we need to learn how acute how applicable it is to humans. a dollar bill) of ingested As2O5 to nearly 4,000 accidental deaths toxicity is measured. The most Who’s to say that a substance kill off a 75 kg human. each year in the United States, common method for identify- lethal to rats would necessarily As2O5 is toxic, but dioxin (often yet it is doubtful that anyone ing the toxicity of a substance have the same effect on humans? labeled the world’s most deadly poison) is about 400 times more would ever think of water as a is LD50, which stands for lethal Nevertheless, LD50 yields deadly. With an ORL-RAT LD poison, since we need to drink it dose–50%. The LD50 indicates valuable information, especially 50 for our very survival! Webster’s the mass of the poison per when it comes to making deci- of only 20 µg/kg, it would only defines poison as “a substance kilogram of sions about what compounds take about 1.5 mg (the mass of that through its chemical action to allow in a certain insecticide this “O” if you cut it out of this usually kills, injures, or impairs or building materials. It is magazine page) to kill an average an organism.” This definition also important to point out human. In comparison, the nerve gas VX has an absorption LD50 of rules out water but certainly that the LD50 of a substance includes a vast number of com- depends quite a bit on the 60 µg/kg. pounds for which human route of exposure: by inhala- Ricin, a protein found in cas- exposure, even at very low tion (breathing in), absorption tor beans that’s been associated levels, can be fatal. (through the skin or eyes), with recent acts and threats The words “most oral ingestion (swallowed), intra- of terror, has about the same deadly” are also open to venous (injected into the vein), toxicity level as dioxin. But all of interpretation. Does this intramuscular (injected into the these toxins would be consid- refer to the substance that muscle), subcutaneous (injected ered “lightweights” compared to is responsible for the most under the skin), or intraperitoneal the protein-based botulin toxin, deaths each year, or the sub- (injected inside the membrane produced by botulinum bacteria and associated with botulism, the VISION stance that requires the smallest that lines the interior wall of the ital most severe form of food poison- dose to cause death? If one is g abdomen). DI ing. It’s arguably the most deadly referring to the substance that body weight necessary to kill If one looks up the LD50 for causes the most deaths world- 50% of a given population. arsenic, for example, it is listed poison in the world. With an LD50 in the range of 5–50 ng/kg, it is wide each year, the poison would Because individuals in any popu- as ORL-RAT LD50 763 mg/kg nearly 1,000 times as toxic as have to be tobacco. It has been lation will have a range of toler- and IPR-RAT LD50 13 mg/kg. estimated that 500,000 people ance levels to any given toxin, This means that a rat ingesting dioxin. die each year of tobacco-related it would be difficult to quantify 763 mg (about 3/4 of a gram) illnesses in the United States LD100 (the dose that would kill of arsenic per kilogram of its 2 Chemmatters, FEBRUARY 2010 www.acs.org/chemmatters ® Vol. 28, No. 1 february 2010 DEPARTMENTS Question from the Classroom 2 Battling Wildfires: By Bob Becker When Water Won’t Cut It 10 What is the most deadly poison in the world? By Sherry Karabin To put out wildfires, firefighters use a variety Did You Know? 4 of chemical solutions. Learn about how these solutions work. Scientists create the world’s smallest transistor; nitrogen oxides Natural ReSOURCeS CONServation SeRVICe, AUBURN, ALA. contribute significantly to the ozone hole. Green Gasoline: Fuel from Plants 13 Profiles in Chemistry: By Michael Schirber Chris Pollock, Chemistry Gasoline can be produced from plants, and even Graduate Student 18 plant leftovers. It is called green gasoline, it may By Dan Risch never run out, and it is good for the environment. Chris Pollock shares his passion for chemistry RSITY e and explains how his research activities may UNIV lead to better drugs to treat cancer. I k MSON LS e e CL LSI e CI ke MI I FEATURES k LS e LSI e The Many Colors of Blood 5 CI ke By Diana Lutz MI Blood can come in many colors. Blue, green, purple, it all depends on the The Makeup of Mineral Makeup 16 animal. Learn about the chemistry inside the blood that produces these different colors. By Jane Andrew Mineral makeup products are one of the hottest trends in cosmetics. Anesthesia: Chemistry in the Are they better for your skin than regular makeup? Operating Room 8 By Claudia M. Caruana TEACHERS! Thanks to drugs called anesthetics, surgery and find your complete other medical procedures are pain-free. How were teacher’s guide for this issue at these “miracle” drugs discovered and how do www.acs.org/chemmatters they work? k ISTOC Production Team education Division Subscriber Information the cautions contained in the text, or from not Patrice Pages, Editor Mary Kirchhoff, Director Prices to the United States, Canada, and following standard safe laboratory practices. Cornithia Harris, Art Director Terri Taylor, Assistant Director, K–12 Science Mexico: $14.00 per subscription. Inquire Therese Geraghty, Copy Editor about bulk, other foreign rates, and back All rights reserved. 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