The fixed-dose procedure (FDP), proposed in 1992 by the British Toxicology Society, is a method to assess a substance's acute oral toxicity.[1][2]
In comparison to the older LD50 test developed in 1927, this procedure produces similar results while using fewer animals and causing less pain and suffering.[3] As a result, in 1992 this test was proposed as an alternative to the LD50 test by the Organisation for Economic Co-operation and Development under OECD Test Guideline 420.[4] However, the U.S. Food and Drug Administration has begun to approve non-animal alternatives in response to research cruelty concerns and the lack of validity/sensitivity of animal tests as they relate to humans.[5][6]
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Fracking explained: opportunity or danger
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Transcription
What is hydraulic fracturing – or fracking ? Since the industrial revolution our energy consumption has risen unceasingly. The majority of this energy consumption is supplied by fossil fuels like coal or natural gas. Recently there has been a lot of talk about a controversial method of extracting natural gas: Hydraulic fracturing or fracking. Put simply, fracking describes the recovery of natural gas from deep layers inside the earth. In this method, porous rock is fractured by the use of water, sand and chemicals in order to release the enclosed natural gas. The technique of fracking has been known since the 1940s. Nonetheless, only in the last ten years has there been quite a “fracking boom”, especially in the USA. This is because most conventional natural gas sources in America and on the European continent have been exhausted. Thus prices for natural gas and other fuels are rising steadily. Significantly more complicated and expensive methods, like fracking, have now become attractive and profitable. In the meantime, fracking has already been used more than a million times in the USA alone. Over 60% of all new oil and gas wells are drilled by using fracking. Now let’s take a look at how fracking actually works: First, a shaft is drilled several hundred meters into the earth. From there, a horizontal hole is drilled into the gas-bearing layer of rock. Next, the fracking fluid is pumped into the ground using high-performance pumps. On average, the fluid consists of 8 million liters of water which amounts to about the daily consumption of 65,000 people. plus several thousand tons of sand and about 200,000 liters of chemicals. The mixture penetrates into the rock layer and produces innumerable tiny cracks. The sand prevents the cracks from closing again. The chemicals perform various tasks among other things, they condense the water, kill off bacteria or dissolve minerals. Next, the majority of the fracking fluid is pumped out again. And now the natural gas can be recovered. As soon as the gas source is exhausted, the drill hole is sealed. As a rule, the fracking fluid is pumped back into deep underground layers and sealed in there. However, fracking is also associated with several considerable risks. The primary risk consists in the contamination of drinking water sources. Fracking not only consumes large quantities of fresh water, but in addition the water is subsequently contaminated and is highly toxic. The contamination is so severe that the water cannot even be cleaned in a treatment plant. Even though the danger is known and theoretically could be managed, in the USA already sources have been contaminated due to negligence. No one yet knows how the enclosed water will behave in the future, since there have not yet been any long-term studies on the subject. The chemicals used in fracking vary from the hazardous to the extremely toxic and carcinogenic, such as benzol or formic acid. The companies using fracking say nothing about the precise composition of the chemical mixture. But it is known that there are about 700 different chemical agents which can be used in the process. Another risk is the release of greenhouse gases. The natural gas recovered by fracking consists largely of methane, a greenhouse gas which is 25 times more potent than carbon dioxide. Natural gas is less harmful than coal when burned. But nonetheless, the negative effects of fracking on the climate balance are overall greater. Firstly, the fracking process requires a very large consumption of energy. Secondly, the drill holes are quickly exhausted and it is necessary to drill fracking holes much more frequently than for classical natural gas wells. In addition, about 3% of the recovered gas is lost in the extraction and escapes into the atmosphere. So how is fracking and its expected benefits to be assessed when the advantages are balanced against the disadvantages? When properly employed, this technique offers one way in the short to medium term for meeting our demand for lower-cost energy. But the long-term consequences of fracking are unforeseeable and the risk to our drinking water thus should not be underestimated. Subtitles by the Amara.org community
See also
References
- ^ Stallard, N.; Whitehead, A. (2 July 2016). "Reducing animal numbers in the fixed-dose procedure". Human & Experimental Toxicology. 14 (4): 315–323. doi:10.1177/096032719501400401. PMID 7598991. S2CID 37663587.
- ^ Walum, E (April 1998). "Acute oral toxicity". Environmental Health Perspectives. 106 (Suppl 2): 497–503. doi:10.1289/ehp.98106497. JSTOR 3433801. PMC 1533392. PMID 9599698.
- ^ van den Heuvel, M.J.; Clark, D.G.; Fielder, R.J.; Koundakjian, P.P.; Oliver, G.J.A.; Pelling, D.; Tomlinson, N.J.; Walker, A.P. (January 1990). "The international validation of a fixed-dose procedure as an alternative to the classical LD50 test". Food and Chemical Toxicology. 28 (7): 469–482. doi:10.1016/0278-6915(90)90117-6. PMID 2210519.
- ^ Stallard, N; Whitehead, A; Ridgway, P (2 July 2016). "Statistical evaluation of the revised fixed-dose procedure". Human & Experimental Toxicology. 21 (4): 183–196. doi:10.1191/0960327102ht239oa. PMID 12099620. S2CID 45430481.
- ^ "Allergan Receives FDA Approval for First-of-Its-Kind, Fully in vitro, Cell-Based Assay for BOTOX® and BOTOX® Cosmetic (onabotulinumtoxinA)" (Press release). Allergan. June 24, 2011. Retrieved May 19, 2020.
- ^ Gaul, Gilbert M. (12 April 2008). "In U.S., Few Alternatives To Testing On Animals". The Washington Post.
Further reading
- Whitehead, A.; Curnow, R.N. (April 1992). "Statistical evaluation of the fixed-dose procedure". Food and Chemical Toxicology. 30 (4): 313–324. doi:10.1016/0278-6915(92)90009-a. PMID 1628867.
- Lipnick, R.L.; Cotruvo, J.A.; Hill, R.N.; Bruce, R.D.; Stitzel, K.A.; Walker, A.P.; Chu, I.; Goddard, M.; Segal, L.; Springer, J.A.; Myers, R.C. (March 1995). "Comparison of the up-and-down, conventional LD50, and fixed-dose acute toxicity procedures". Food and Chemical Toxicology. 33 (3): 223–231. doi:10.1016/0278-6915(94)00136-c. PMID 7896233.
- Yam, J.; Reer, P.J.; Bruce, R.D. (January 1991). "Comparison of the up-and-down method and the fixed-dose procedure for acute oral toxicity testing". Food and Chemical Toxicology. 29 (4): 259–263. doi:10.1016/0278-6915(91)90023-Z. PMID 2040488.
- Stallard, Nigel; Whitehead, Anne (9 April 2019). "A Statistical Evaluation of the Fixed Dose Procedure". Alternatives to Laboratory Animals. 32 (2_suppl): 13–21. doi:10.1177/026119290403202s05. PMID 15601221. S2CID 46160911.
- Stallard, N.; Whitehead, A. (2 July 2016). "The fixed-dose procedure and the acute-toxic-class method: a mathematical comparison". Human & Experimental Toxicology. 14 (12): 974–990. doi:10.1177/096032719501401206. PMID 8962748. S2CID 78559.
- Stallard, Nigel; Whitehead, Anne; Indans, Ian (2 July 2016). "Statistical evaluation of an acute dermal toxicity test using the dermal fixed dose procedure". Human & Experimental Toxicology. 23 (8): 405–412. doi:10.1191/0960327104ht465oa. PMID 15346722. S2CID 26925263.
- Ellard, GA (November 1999). "The evaluation of rifampicin bioavailabilities of fixed-dose combinations of anti-tuberculosis drugs: procedures for ensuring laboratory proficiency". The International Journal of Tuberculosis and Lung Disease. 3 (11 Suppl 3): S322-4, discussion S351-2. PMID 10593711.