Top Document: Sci.chem FAQ - Part 2 of 7 Previous Document: 9. Traditional General Chemistry Information Sources See reader questions & answers on this topic! - Help others by sharing your knowledge 10.1 Where can I find Material Safety Data Sheets? Most suppliers of chemicals will provide a MSDS on request if you are a customer. Several major chemical suppliers have combined their own MSDS sheets and issued major compilations, eg Sigma-Aldrich [1] ( available on CD-ROM or Magnetic Tape for $1,650), which may be available in the library. If a librarian can not locate the MSDS database, then try the Health and Safety Officer, who should know where to find MSDS. Larger organisations often purchase a compilation and make it available on a computer network for in-house use. The US Department of Defence CD-ROM of approximately 200,000 MSDS is available for approximately $100. 10.2 Where can I find hazard information for a chemical? Chemical suppliers usually include common hazard information in their catalogues. Merck and Hawley also list some information. Large compilations include Sax, Fire Protection Guide to Hazardous Materials [2], Sigma-Aldrich Library of Chemical Safety Data [3], CRC Handbook of Laboratory Safety [4], and Hazards in the Chemical Laboratory [5]. It is very important to realise that hazard information is frequently updated, and so information should be complemented with an online search of safety databases. If the chemical is already being used at your site, it is probable that the Safety Officer or Laboratory Manager already have the required information. The Handbook of Reactive Chemical Hazards [6], can be used to check for possible hazardous reactions. Highly toxic, radioactive, and carcinogenic compounds require special precautions, and the Safety Officer or Laboratory Manager should be able to provide the appropriate resources to ascertain if the compound can be handled safely. 10.3 Where can I find detailed safety & toxicity data? The very first question you should ask is, "Am I qualified to assess the data?". If the answer is no, then your best option is to locate somebody who is. This can be a Health and Safety Officer, staff of an appropriate government organisation (eg OSHA, NIOSH ), or a specialist consultant. Most institutions have a policy of ensuring workers are given sufficient information about hazards to ensure they can make an informed decision. There are several major compilations that are usually found in libraries, including RTECS, Sax, and the three-volume Sigma-Aldrich Library of Regulatory and Safety Data [7]. In general, because safety information can become obsolete rapidly, these should only be used as an introductory guide, and they should be complemented with either an on-line search or consultation with an expert. Detailed information for unusual chemicals is often difficult to locate in the published literature, and may only be available to qualified professionals in the health and safety fields. Sometimes the toxicity has to be inferred from published information on related compounds, and such assessments should always be performed by experts. 10.3 Where can I find occupational exposure limits? There are several organisations responsible for establishing the occupational exposure limits. The values used most extensively in industry, but also the most controversial, are those of the ACGIH. Their TLVs and Biological Exposure Indices [8] have been used in many countries as initial guidelines until relevant local expertise can assess their suitability. They are also misused, despite the clear warnings in the front of the booklet. The US Government also has Permissible Exposures Limits set by the Dept. of Labor Occupational Safety and Health Administration, and Recommended Exposure Limits set by the US National Institute for Occupational Safety and Health. The Deutsche Forschungsgemeinschaff Maximum Concentrations in the Workplace are often also used. The ACGIH publishes an excellent compilation of all these limits [9], thus facilitating a review of how experts perceive the occupational hazards. The International Labour Office in Geneva publishes a comprehensive " Encyclopedia of Occupational Health and Safety " which also covers chemicals [10]. 10.5 What is the most poisonous compound? " All substances are poisons. There is not one that is not a poison. The correct dose differentiates a poison and a remedy". (Paracelsus 1493-1541) The McGraw Hill Encyclopedia of Science and Technology [11] lists the following table: "Approximate Median Lethal Doses of Some Toxins per kg of Bodyweight" Toxin Dose Test Animal tetanus 1 nanogram mouse, probably human botulinal neurotoxin 1 nanogram mouse, human shigella 1 nanogram monkey, human shigella 1 microgram mouse ricin 1 microgram human diphtheria 100 nanograms human diphtheria 1.6 milligrams mouse Ricin is a toxin lectin and hemagglutinin isolated from the castor bean. Merck reports the lethal dose in mice as 1 microgram of ricin D nitrogen (ip) per kg, and that ricin molecular weight is about 65,000. Ricin has been shown to contain four lectins, of which the RCL III (aka Ricin D ) and RCL IV are the toxins. Merck also reports the following LD50 per kg of bodyweight:- Toxin Dose Test Animal palytoxin 60 nanograms dog (iv) ( from coral ) 450 " mouse (iv) ( C129H223N3054 ) 50-100 " " (ip) saxitoxin 3-5 micrograms mouse (iv) ( from shellfish ) 10 " " (ip) ( [C10H17N7O4]2+ ) 263 " " (oral). tetrodotoxin 10 " mouse (ip) ( from globefish ) aflatoxin M1 332 micrograms duckling (oral) aflatoxin M2 1.2 milligrams " " aflatoxin B1 364 micrograms duckling (oral) aflatoxin B2 1.6 milligrams " " aflatoxin G1 784 micrograms " " aflatoxin G2 3.4 milligrams " " The complex structure of palytoxin is shown in Merck, and it is listed as the most toxic non-proteinaceous substance known. 10.6 Where can I find laboratory safety guides? The journals "Chemical Health and Safety", and "Journal of Chemical Education" have articles on many aspects of laboratory safety. Safety Officers and Laboratory Managers at educational institutions and companies are likely to have several guides, and a polite request should obtain a loan or copy of one, even if you aren't at that institution. There are several useful books. The most popular are:- CRC Handbook of Laboratory Safety [4] - good general discussion of laboratory safety issues. Hazards in the Chemical Laboratory [5] - good general discussion of laboratory safety concepts with data. Guidelines for Laboratory Design: Health and Safety Considerations [12]. - modern design concepts for new and refurbished laboratories. Laboratory Health and Safety Handbook: A Guide for the Preparation of a Chemical Hygiene Plan [13] - such a plan is required by OSHA, and additional examples may also be available from chemistry departments of local educational institutes. 10.7 Are contact lenses a hazard in laboratories? There are a lot of myths about the occupational use of contact lenses, many of which relate back to a Bethlehem Steel welder in Baltimore who, on the 26 July 1967, accidentally caused an arc flash that hit his hard contact lens. He waited until the next day to report eyesight problems, and an ophthalmologist found severe ulcerations on his cornea, but attributed the damage to the wearing of the hard lenses for 17-18 hours after the incident. The cornea healed completely in a few days, with no permanent vision loss, and investigators found no link between the damage and the arc flash, but the myth of the welder removing parts of the cornea with the lens, and consequently being permanently blinded, continues [14]. The banning of contact lenses from modern chemical laboratories is being reconsidered in the light of increasing evidence that case-by-case evaluations are more appropriate. Routine wearers of contact lenses may suffer " spectacle blur " when they switch to spectacles, and this temporary reduction in visual efficiency could result in the misreading of labels. Contact lenses are not eye protection devices, and OSHA believes that if eye hazards are present, appropriate eye protection must be worn instead of, or in conjunction with, contact lenses. There may still be some laboratory environments where the provided personal protection equipment does not protect wearers of contact lenses, and they will remain banned. There are three major areas of concern about the hazards of wearing contact lenses in chemical laboratories. 1. They can hold particulate or liquid material against the cornea. The modern soft contact lenses are considered suitable for most environments, except where heavily contaminated with metal particles. Hard contact lenses are not considered suitable for use in particle-contaminated areas. 2. Contact lenses can be difficult to remove after a chemical splash. This is a concern, and is one reason why wearers of contact lenses in laboratories should be obviously identifiable to first-aid and professional secondary care providers. The copious irrigation procedures with water ( whilst holding the eye open ) that should immediately follow chemical splashes may wash the lenses out, and trained staff can remove any remaining lenses later. Experiments with concentrated sodium hydroxide solution, sulfuric acid, acetic acid, acetone and n-butylamine have shown that contact lenses may actually provide some protection [14]. 3. Contact lenses may absorb and retain chemical vapours. This effect was not observed in the splash experiments above, and soft lenses have been shown to reduce the effect of acids, perhaps because tears can dilute the acid by the time it passes through the lens. Some chemical vapours may be absorbed and retained, but often exposure should be eliminated by personal protection equipment anyway. The January/February 1995 issue of Chemical Health and Safety had three articles on contact lenses, including an excellent article on how to prepare for, and act during, contact lenses emergencies [15]. All three articles note that changing technologies have resulted in improved lenses that may now be acceptable in many modern laboratories, however the merits of each case should be carefully examined before approval. The issue of contact lenses in laboratories is still being carefully reviewed, as there are also legal implications for both employers and employees, and laboratory safety literature should be monitored to obtain the latest perceptions [16,17]. User Contributions:Top Document: Sci.chem FAQ - Part 2 of 7 Previous Document: 9. 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Last Update March 27 2014 @ 02:12 PM
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