F Toxic Chemicals Handbook--MSDS Sources
F‑3 Airborne Dusts
F‑5 Other Substances
F‑6 Handling Toxic Substances
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.