F Toxic
Chemicals Handbook--MSDS Sources
F‑1 Gases
F‑2 Vapours
F‑3 Airborne Dusts
F‑4 Vesicants
F‑5 Other Substances
F‑6 Handling Toxic Substances
F-7 Allergies
As long ago as
the 15th century, Paracelsus recognized that all materials are toxic to some
degree. Dosage determines whether a
substance is harmless, an essential food or a medicine, or whether it is a
poison (with the exception of substances causing immune system
sensitization). A complex relationship
exists between a substance and its biological effects; some factors to be
considered are level of exposure, duration of exposure, route of entry into the
body, age, sex, race, stage in the reproductive cycle and even lifestyle. Because of these many factors involved, all
chemicals should be treated with respect for their known or potential
hazards. Skin, eyes and respiratory
tract should always be protected from exposure by the use of protective
clothing, safety glasses and ventilation equipment. Eating, drinking and smoking should never be allowed in an area
where chemicals are handled. Personal
hygiene practices such as always washing the hands after handling chemicals are
also very important.
A substance may
have a very great inherent toxicity (ability to cause biological damage if
absorbed by the body) but it will not be a hazard if properly handled and
therefore does not enter the body.
Possible routes of entry are absorption by the eyes or skin, through the
respiratory tract and via the digestive tract.
By far the most important of these is by inhalation into the respiratory
tract. The potential for such exposure
can be greatly reduced by the proper use of a fume hood. Many substances are readily absorbed by the
eyes or through intact skin (cuts, rashes or other sores may make entry even
easier). Solvents in general and even
elemental mercury can be absorbed directly through intact skin. Use of gloves can reduce this exposure but
gloves made of a material resistant to the particular chemicals in use must be
selected. One should also be aware that
gloves, even when new, may have holes in them.
Ingestion into the digestive tract can be avoided with a few simple
precautions. Food or drinks should
never be stored in a chemical lab where they will absorb vapors and should
never be eaten in the laboratory.
Always wash before eating or taking a coffee break. Never pipette by mouth even with non‑toxic
materials since the pipette may be contaminated from previous operations.
When a
hazardous material does contact the body, it may have effects directly at the
site of contact (eg. vesicants which cause chemical "burns"). Once a substance is absorbed by the body it
will to some extent become dissolved in the blood; the substance will then be
carried to every part of the body.
Often toxic materials will be stored or concentrated at various
locations in the body. This factor may
increase their toxicity. Common sites
of concentration are the liver and kidneys where the body is attempting to
metabolise and eliminate them; thus these organs often suffer damage. Another important factor is that metabolites
of foreign substances may be much more toxic than the parent compounds. For example, some PAH's are of low toxicity
but their oxidized metabolites are very much more toxic.
The range of
possible effects of hazardous materials is quite broad. Simple irritant effects at the site of
contact may produce reddening and pain; this is usually reversible but
prolonged or more severe exposure may produce permanent scarring. Compounds which interfere with the bodies'
metabolism may be very deadly poisons in relatively small amounts. Inert gases such as carbon dioxide or
nitrogen can act as simple asphyxiants by displacing the normal oxygen content
of air. Others such as carbon monoxide
act as chemical asphyxiants by combining with hemoglobin in the blood to block
transfer of oxygen to the tissues.
Since carbon monoxide combines with hemoglobin 200 times more strongly
than oxygen, even relatively low concentrations in the air can cause a build‑up
in the blood resulting in asphyxiation.
Some individuals when exposed to a substance develop an immune system
hypersensitivity such that subsequent exposure even to extremely small amounts
of the substance can produce wide-ranging effects. These effects range from simple rashes, wheezing and runny nose
("hay fever") to sudden death (see Section F-7). Many substances can cause mutations in
genetic material (mutagens). These
changes may result in the later production of cancer (carcinogens) or, if they
occur in the fetus, may cause spontaneous abortion or birth defects
(teratogens). Both men and women can be
affected by reproductive toxins that interfere with the normal production of
sperm or egg cells resulting in lowered reproductive capacity or
sterility. Pregnant women, particularly
early in the pregnancy (which might be before the pregnancy is apparent), are
at greater risk. It should be kept in
mind that any substance may have more than one of these effects. In addition to these chemical problems,
persons working with human fluids, animals or tissue cultures may be exposed to
biological hazards such as aids, hepatitis, cancer cells, rabies, allergy
problems, etc.
The timing of effects from
exposure to hazardous substances varies greatly. Obvious effects from short‑term exposure occurring within
24 hours (acute) are usually reversible.
Long-term exposure to sub‑acute doses may result in chronic
effects, which often produce permanent damage.
These effects may result from slow concentration of a substance in the
tissues until it begins to produce an obvious effect or there may be an
accumulation of minor damage until obvious symptoms begin to appear. In this latter case, irreversible damage may
be done before it becomes noticeable.
As an example, acute exposure to carbon monoxide may result in
unconsciousness but after removal from the exposure, complete recovery is
possible. However, long-term exposure
to small amounts of carbon monoxide will result in permanent hardening of the
arteries and heart disease. For
exposure to carcinogens, the resulting cancer may not appear for 10 to 40 years
after exposure thus adding a special type of danger to these substances. Another potential long-term problem is
behavioural changes. A significant
correlation between solvent exposure and feelings of tiredness, sickness, nausea
and headache has been demonstrated; some of these may be allergy types of problems.
The degree of
effects depends on the inherent toxicity of the substance and the amount of
exposure (for airborne contaminants, concentration and length of time of
exposure). For example, exposure to low
amounts of an organic phosphate pesticide may result in dizziness, nausea and
headache, which are reversible, but greater exposure may result in
unconsciousness and death. A further
complication is synergistic effects; with combinations of substances the overall
effects may be much greater than the expected additive effects. For example, exposure to tobacco smoke and
asbestos results in a cancer rate at least ten times that expected from the
additive effect. Also, in the presence
of chloroform, phosgene will be produced in the burning zone of cigarettes. Interactive factors such as these are still
largely unknown.
A list of toxic
properties can be found in "Hazardous Chemicals: Information and Disposal
Guide"; a copy of this book has been provided to each laboratory in the
Chemistry department. Make sure that you know where it is
located.
Material Safety
Data Sheets are required by law to be readily available for all potentially
harmful chemicals in the laboratory.
Hard copy MSDSs of some products from BDH are available in ABB365. The
CCINFO MSDS database is available on the internet at http://ccinfo.wed.ccohs.ca. Other MSDS's are available at
http://www.mac.ca/riskmanagement.
Almost all
chemical substances that are dealt with in the laboratory are to some degree
toxic to humans when ingested as liquids or solids or inhaled as gases or
dusts. It makes sense to take normal
precautions with all substances to keep them out of mouth, nose, and eyes, and
even off the skin. Some poisons can be absorbed into the body through the skin;
others, known as vesicants, can attack the skin and underlying tissues causing
dangerous chemical "burns" which are very painful and slow to heal. The Ontario Ministry of Labour has
regulations governing "Designated Substances"; these are discussed in
Section 1‑6. Certain substances,
because of their high toxicity or their insidious action, deserve special
mention. These are discussed in the
following sections.
F-1. BE AWARE OF TOXICGASES.
Carbon monoxide
(CO) is a highly toxic gas that is universally recognized as dangerous because
it is colourless, odourless, and tasteless; the physiological danger symptoms
often come too late to give warning. Since carbon monoxide combines with the
hemoglobin in the blood approximately 200 times more strongly than oxygen, even
relatively low concentrations can cause suffocation. Chronic exposure to low levels of carbon monoxide also causes
irreversible damage to the heart and circulatory system. Also in this category of toxicity are H2S,
HCN, NO, PH3, AsH3, SbH3, and COCl2
(phosgene). Even though H2S can be detected by the human nose at
exceedingly low concentrations, there is evidence that higher concentrations of
this gas quickly deaden the sense of smell.
Therefore electronic sensors should be used if higher concentrations of
H2S might occur. H2S
is toxic at lower concentrations than CO.
Other particularly hazardous gases or vapours are: acrolein, halogens (F2,
Cl2, Br2, I2), hydrogen halides (HF, HCl, HBr,
HI), methyl halides (CH3Cl, CH3Br), NO2, O3
(ozone), CS2, SO2, CH2N2
(diazomethane), and metal carbonyls. Most of the above gases are extremely
dangerous or fatal for exposures of a few minutes at concentrations on the order
of 100 ppm (parts per million). The "maximum allowable concentration"
(often abbreviated MAC) is on the order of 1 ppm for most of these gases,
although for phosphine and its analogues the MAC is only 0.05 ppm. Ammonia,
ethylene oxide, ethyleneimine, and ketene are also toxic. All of the above
substances should only be handled in a fumehood.
F‑2. SOLVENT AND REAGENT VAPOURS
The vapours of
solvents, particularly benzene, chlorinated (and brominated and iodinated)
hydrocarbons, and esters of mineral acids (e.g., dimethyl sulfate) are more
dangerous than is commonly recognized.
Benzene is a cumulative poison affecting the blood‑forming
tissues; it has been claimed to cause leukemia. Chlorinated hydrocarbons affect the heart, the circulatory
system, and the liver. Even saturated hydrocarbon vapours can have toxic
effects. The vapours of nearly all organometallic compounds such as tetraethyl
lead and dimethyl mercury are very toxic at very low concentrations; the vapour
of osmium tetroxide is extraordinarily toxic with an MAC as low as 0.002
ppm. Prolonged inhalation of mercury vapour may result in damage to
kidneys, eyes, nervous system and other organs. The saturation vapour pressure
of mercury at room temperature (1.8 x l0-3 torr or about 20 mg per
cubic meter) is about 400 times the MAC
of 0.05 mg/m3.
F‑3. AIRBORNE DUSTS
Beryllium metal and its
compounds (MAC: 0.002 ppm), heavy‑metal compounds, naphthylamines, and
certain alkaloids present a high degree of hazard when they can be inhaled as
dusts. Beryllium has a complex
toxicology; some effects of chronic exposure may be delayed as long as 15
years. Very fine dusts should be
handled very carefully in a fume hood; it may be necessary to open the sash to
decrease the flow velocity in order to prevent dusts from blowing around.
F.4. VESICANTS (CHEMICAL BURNS)
Liquid bromine,
bis(β‑chloroethyl)sulfide ("mustard gas"), the nitrogen
mustards (β-haloethylamine
derivatives), α‑halo ketones and esters, benzylic and allylic
halides, and phenol attack the skin on contact, producing chemical burns and in
some cases internal poisoning as well. Many reactive alkylating agents can
cause bad skin burns and result in allergic reactions if this contact is
repeated at a later date.
F‑5. OTHER TOXIC SUBSTANCES
Among inorganic compounds, cyanides,
mercuric salts (which even in small quantity may produce irreversible kidney
damage, and possible death) other heavy metal compounds (Ba, Pb, Cu, Ag, Zn,
Cd, Co, Ni, Os, and others), chromates, and beryllium salts must be mentioned.
Ferricyanides, ferrocyanides, and thiocyanates are less hazardous than cyanide
salts as they do not give rise to free HCN in the body. Beryllium compounds may be absorbed in
dangerous amounts through the skin.
Oxidizing salts (AgNO3, chromates) may produce skin
damage. Poisonous organic compounds include certain alkaloids and biologically
produced toxins, organometallic compounds, compounds of hydrazoic acid, esters
of inorganic acids such as diisopropyl fluorophosphate, tetraethyl
pyrophosphate, dimethyl sulfate, and methyl iodide; several of these can
penetrate unbroken skin. Aromatic amines such as aniline and nitro compounds
such as nitrobenzene are particularly dangerous because they are readily
absorbed through the skin, where they react in the blood to convert hemoglobin
to methemoglobin; in addition they can produce severe damage to the nervous
system. Less toxic but still significantly so are benzene, chlorinated
hydrocarbons, methanol, and butanol. β-Naphthylamine, which can be absorbed
through the skin, has been incriminated as a human carcinogen; one should also
be aware that crude α‑naphthylamine may contain some of the
isomer. These are especially dangerous
as dusts that may be inhaled. Other
known human carcinogens are benzo[a]pyrene and certain other aromatic fused‑ring
hydrocarbons. Dimethyl sulfate and
other alkyl sulfates are very poisonous; severe inflammation of the eyes, nose
and respiratory system are caused by hydrolysis of the compounds to sulfuric
acid. These agents have also been shown
to produce respiratory system cancers in rodents exposed to concentrations of
0.5 ppm. Material Safety Data Sheets must be readily available in the
laboratory as a source of known toxicological information.
Knowing the toxicity of all substances used in
the laboratory is the responsibility
of the researcher including the lab Supervisor.
Radioactive
substances may involve exceptional dangers which are beyond the scope of this
review. Examples of radioisotope use are isotope tracer studies, activation
analysis with neutron irradiation, fission and nuclear decay studies, "hot‑atom"
chemistry, and Mossbauer spectroscopy. In
all cases Health Physics (ext. 23365) must be consulted before such an experiment is undertaken;
the handling, storage and use of any radioisotope is subject to approval and
review by the Health Physics Committee.
F‑6. HANDLING TOXIC SUBSTANCES
When dealing
with toxic or potentially toxic substances, take proper and reasonable
precautions:
a. ASSUME
THAT ANY SUBSTANCE IS TOXIC unless you know positively to the contrary;
when in doubt, consult the Material Safety Data Sheet, the Merck index or other
toxicology reference works (see Section K or consult the Occupational Health
and Safety Office in MUMC).
b. Do not pipette any
solutions by mouth.
c. Use rubber gloves and a face mask when dealing
with any substance that may attack or penetrate the skin.
d. All
operations utilizing or giving off toxic or malodorous gases or vapours must be
carried out in the fume hood. Special
procedures during weighing may also be required.
e. Never evaporate solvents
other than water in the open; use a rotary evaporator or other still.
f. Highly
hazardous gases (e.g., Cl2, phosgene) should be obtained in small
cylinders and used only in the hood. When not in use they should be stored in a
well ventilated area or returned.
g. Operations
involving beryllium or thallium and their compounds or other substances with
highly dangerous dusts should be performed in a "dry box" or glove
bag. Wear a dust mask.
h. It is legally
required that all vessels containing chemicals (hazardous or otherwise) are
properly labelled. Never place vessels
containing hazardous volatile chemicals or unlabelled or unstoppered vessels
containing any chemicals in a
refrigerator.
i. In the event
of mercury spills, regardless
of how small, pick up as much of the mercury as possible (use a glass or metal
capillary tube connected to a trap bottle and an aspirator). In the case of
large spills, call a member of the Safety Committee for assistance or advice.
Be particularly concerned about mercury in the vicinity of heated objects
(steam lines, steam radiators, hot plates) where the vapour pressure will be
much higher. Use a mercury spill kit as directed. Alternatively, sprinkle any contaminated area with "flowers
of sulfur", and after 48 hours sweep up as much of it as possible. Place
sweepings in a container and arrange for it to be picked up for disposal as
described in Section G-3. Inaccessible
mercury droplets in crevasses should be covered lightly with sulfur. Waste
mercury (including that recovered from spills) should be accumulated in a
stoppered bottle. Do not leave mercury in uncovered or unstoppered vessels.
F-7 Allergies (Immune System Sensitization)
The phenomenon of allergy (immune system sensitization) is very different from ordinary toxic effects. It is the exaggerated response of the immune system, rather than the inherent toxicity of the material, which causes the harmful effects‑‑one does not normally think of peanuts, for example, as being deadly! Virtually any chemical can cause these effects that are becoming more common in modern society. On initial exposure there will be no obvious effect, however the immune system remembers this contact and subsequent exposure may result in an exaggerated immune system response. The major effect is the release of large amounts of histamine within the body which results in the dilation of blood vessels and release of fluids into the tissues. The effects of this action are very wide ranging. Minor problems such as runny nose and watery eyes ("hay‑fever") and itching or rashes are most common but stiff muscles, sore joints, difficulties with focusing the eyes, poor concentration, poor memory and mental confusion may also occur. Acid stomach and chest pains combined with difficult breathing (which can mimic a heart attack) may also occur. At the worst, "anaphylactic shock" may cause total collapse of the circulatory system; this can result in loss of consciousness and death within a few minutes of exposure if emergency treatment is not obtained (treatment consists of injection of adrenalin). Persons who have allergies or suspect they are having an allergic response to something in the laboratory should be aware of the potential for very serious effects.