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Plastics
Published in Ronald M. Scott, in the WORKPLACE, 2020
A sampling of commonly used catalysts is shown in Table 7.6. Reactions to form addition polymers very often proceed by a free radical mechanism. Such a mechanism requires a source of free radicals, structures with unpaired electrons, to initiate the chemical reaction. Most often, organic peroxides are used. Around 50 different such compounds are available, primarily peresters and percarbonates. Benzoyl peroxide and MEK peroxide are representative and frequently encountered examples. Peroxides share similar properties, all being strong oxidizing agents capable of reacting violently with appropriate substances. Skin irritation and burns are likely on contact with peroxides, and severe eye damage is possible. Benzoyl peroxide is a sensitizer; chronic exposure leads to an allergic rash. It has a PEL of 5 mg/m3, and an IDLH level of 1000 mg/m3. Both from the standpoint of hazard due to direct contact and because of a potentially violent reaction, waste or spilled peroxides should be diluted with water, and any rags used in the cleanup of spills similarly should be put in water. The rate of chemical decomposition of the compounds increases with temperature, and contact with combustibles such as paper or wood can lead to fires.
Polymers
Published in Ronald Scott, of Industrial Hygiene, 2018
A sampling of commonly used catalysts is shown in Table 20.6. Reactions to form addition polymers very often proceed by a free radical mechanism. Such a mechanism requires a source of free radicals, structures with unpaired electrons, to initiate the chemical reaction. Most often organic peroxides are used. Approximately 50 different such compounds are available, primarily peresters and percarbonates. Benzoyl peroxide and methylethylketone peroxide are representative and frequently encountered examples. Peroxides share similar properties, all being strong oxidizing agents capable of reacting violently with appropriate substances. Skin irritation and burns are likely on contact with peroxides, and severe eye damage is possible. Benzoyl peroxide is a sensitizer, chronic exposure leading to an allergic rash. It has a PEL of 5 mg/m3 and an IDLH level of 1000 mg/m3. From the standpoint of hazard due to direct contact and because of a potentially violent reaction, waste or spilled peroxides should be diluted with water, and any rags used in the cleanup of spills similarly should be put in water. The rate of chemical decomposition of peroxides increases with temperature, and contact with combustibles such as paper or wood can lead to fires.
Household and Personal Care Products: Cleaning up and Looking Good
Published in Richard J. Sundberg, The Chemical Century, 2017
Acne is a common skin problem caused by several factors. There is hyperkeratinization and obstruction of sebaceous gland follicles, followed by infection with the organism Propionibacterium acnes. This results in inflammation and can lead to scarring. The skin eruptions are called comedones. The sebaceous glands are under hormonal control and acne is especially common in adolescents. Mild case of acne can be treated with topical retinoids, benzoyl peroxide, azelaic acid, or topical antibiotics. Systemic courses of antibiotics are also used. Hormonal treatments that have estrogenic and antiandrogenic effects (similar to birth control pills—see Section 15.3.3) are sometimes effective for females. The most effective treatment for severe acne is the cis isomer of retinoic acid, called isotretinoin, but it is a potent teratogen and strict regulation is required for its prescription. The brand name product Accutane, approved by the FDA in 1982, was the largest selling drug of the Swiss drug company Roche for a time. Generic versions have been available since 2001. Because of the powerful teratogenicity of the drug, special controls have been put in place for its prescription. During the 1980s, package warnings and letters to physicians were used to alert patients. Nevertheless, it is estimated that there were 4 instances of pregnancy for every 1000 prescriptions, which were running at 200,000 per year. With the availability of the drug in generic form, the FDA and manufactures agreed to establish an internet-based registry system whereby distributers, pharmacies, physicians, and patients are registered. Only those properly registered can distribute, prescribe, dispense, and receive the drug. Monthly confirmation of a pregnancy test and follow-up of any instance of pregnancy are required. This represents the most thorough implementation of a system for control of a potentially harmful drug yet tried.21 In the EU, there are similar mandatory pregnancy tests before and during treatment, with immediate discontinuence in the case of pregnancy.22 In the public media, isotretinoin (as Accutane) has been associated with adolescent depression and suicide. The possible association is complicated by the fact that acne itself can cause social and psychological problems that may lead to depression. The scientific information that is available is contradictory and inconclusive.23 Some ocular side-effects have also been documented for isotretinoin, most commonly blurred vision, keratitis and opacity, eye dryness, and reduced night vision.24
Formulation and evaluation of niosomes-based chlorpheniramine gel for the treatment of mild to moderate skin allergy
Published in Journal of Experimental Nanoscience, 2022
Urooj Afreen, Khairi Mustafa Fahelelbom, Syed Nisar Hussain Shah, Akram Ashames, Uzma Almas, Shujaat Ali Khan, Muhammad Arfat Yameen, Naveed Nisar, Muhammad Hassham Hassan Bin Asad, Ghulam Murtaza
Skin irritation study of formulated niosomal gel of CPM showed, mean skin irritation score of 0.02 ± 0.01 confirming non irritancy, and safety of gel for topical use on human skin without producing any sign of irritation, i.e. redness, lesion, abrasion or erythema [61]. The effects were in accordance with those of Benzoyl peroxide niosomal gel skin irritation test having score of 1.13 ± 0.21 being safe for skin use [31].