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Sci.chem FAQ - Part 2 of 7
Section - 10. Traditional Laboratory and Chemical Safety Information Sources

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Top Document: Sci.chem FAQ - Part 2 of 7
Previous Document: 9. Traditional General Chemistry Information Sources
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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].
   

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