I & D U S T R I A LA X D ENGINEERILt’G CHEJTISTRY
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Vol. 17, No. 8
Industrial Poisoning by Aromatic Compounds‘ By D. H. Killeffer, Associate Editor 19
E. 2 4 T ~ST.,NEW YORK,N. Y.
LEANLINESS is said to be next to godliness. Certainly it is a prerequisite to the efficient production of those organic compounds involving the benzene ring in their structure. The two pictures presented by the American industry in these products now and eight, six, even five years ago show in a striking manner the close relation that exists between cleanliness and profits. Without the introduction of efficient schemes for preventing the many so-called “blues” and “itches” by enforcing cleanliness of employees and by providing adequate safeguards against poisoning, it is doubtful if the American organic chemical industry would have survived the keen competition, both a t home and abroad, of the last three years. I n the first American plants the escape of steam from process kettles, bearing with it small but effective quantities of poisonous vapors, was not uncommon. Dusty materials were handled with only the precautions necessary to prevent explosions and with little thought of the effect which the dust itself might have upon the workmen. Clothing worn in the plant consisted usually of an old pair of shoes and an old suit of overalls, hastily put on over street clothes and worn day after day and week after week until they either wore out or were otherwise damaged. Most plants early realized the necessity of first-aid equipment and many provided baths, but there was no compulsion about using them. Usually the employees were foreigners not long in this country, who continued to observe only those hygienic measures which their life abroad dictated and militantly resented any effort to force them to keep clean. Consequently in aniline and dinitrobenzene plants, as well as others where similar hazards were encountered, superintendents considered that their duty had been properly performed if they were able to get out the required production without more than 10 per cent of their men continuously on leave and if such men as were left were able at least to stand up. The introduction into some of the leading plants in this industry of compulsory bathing, compulsory complete changes of clothing on entering and leaving the plant, compulsory medical examinations a t stated intervals, and of keen competition in the sale of products which made efficiency essential has wrought a remarkable change in plant personnel. It is now unusual for men to be kept from work by sickness caused by the compounds which they handle. Occasional accidents necessarily mar otherwise clean records, but no worker need go into such a plant today with more fear of the consequences than into any other industry.
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Types of Poisoning
The most common industrial poisons in this field whose effects are serious are benzene, aniline oil, nitrobenzene, dinitrobenzene, m-nitroaniline, p-nitroaniline, dinitrochlorobenzene, chlorobenzene, the azo derivatives of these, nitrosodimethylaniline, and to a lesser extent the corresponding derivatives of toluene and xylene. Three distinct types of poisoning result from carelessness with these compounds. Benzene produces a genuine anemia, which is most often chronic from small continued doses, but which may be fatal from large doses. -4 distinct cyanosis is produced by the amino and nitro derivatives, which may be fatal and which 1 Received
December 24, 1924.
usually leaves its effect on the individual for some time The third type of poisoning is a skin disorder resulting from constant irritation by the azo compounds and nitrosodimethylaniline in the form of dust. Many persons possess idiosyncrasies for or against these various forms of poisoning to such an extent that the literature of the subject is devoted largely t o oddities rather than to average cases. Hence care must be exercised in any effort to draw general conclusions from a few cases. BENzEhx-Benzene poisoning is most commonly met in refineries where it is handled in quantity a t more or less elevated temperatures and in those industries where it is used as a solvent and must be evaporated out of the finished product. I n a sense it is cumulative, for each exposure to i t lessens one’s resistance in future exposures. Young women are particularly subject to it, and it is extremely dangerous for them to be exposed to benzene vapors during their menstrual periods. In chemical plants where benzene serves as a raw material, it is generally handled in closed systems and is either blown with carbon dioxide (to prevent the formation of explosive mixtures with air), or pumped from one vented tank to another. I n this way few cases of poisoning occur, except when it becomes necessary to enter a tank that has contained benzene to make repairs. The danger in such a case is great and the only adequate precaution is to steam the tank out thoroughly, fill it with water to insure the absence of berfzene vapors, and enter it only after it has been again filled with fresh air by the withdrawal of the water. Even then it is unsafe for a workman t o enter unless provision is made to pull him out if he should collapse. Some arrangement for blowing in fresh air should be provided as an additional safeguard. Poisoning by benzene occurs generally through the breathing of its vapors. Even the washing of one’s hands in it will seldom produce the slightest symptoms unless too much of its vapor is inhaled a t the same time. The symptoms are almost immediate collapse, with difficulty in breathing and sometimes cyanotic symptoms. The blood shows signs of anemia and in severe cases loses the power of coagulation. Lowering of the count of both white and red corpuscles in the blood occurs in chronic cases. The remedies consist in giving the patient plenty of fresh air and a stimulant such as coffee. No exertion should be required and, above all, no alcohol should be given in any form. Blood transfusion is frequently necessary in severe cases. ANILINEA K D SITRO ComonxDs-The poisoning caused by aniline is less rapid in its effect than acute benzene poisoning and usually gives warning of its coming. Except in extreme cases, where the victim is literally bathed in aniline, cyanosis and loss of strength manifest themselves gradually, and do not develop until an hour or so after exposure, although where the patient has been continuously exposed to small quantities symptoms may appear in a shorter time. With aniline poisoning and poisoning by related nitro and amino bodies the poison is as readily absorbed through the skin as through the mucous membranes, which is not the case with benzene. The vapors of aniline that escape from small leaks in apparatus in which it is being distilled and small amounts of the oil spilled upon the clothing and neglected are the principal sources of poisoning.
August, 1925
I-I-DCSTRIAL A S D E-VGI,VEERI.VG CHEMISTRY
The only useful remedies are preventive rather than curative. Ample ventilation of the plant and cleanliness of the body and clothing will prevent most cases of serious poisoning by any of these compounds. I n cases of exposure or cyanosis, the patient should be immediately given a warm bath, showers with warm water and soap being most effective. Clean clothes should then be put on. Where exposure has resulted in collapse, immediate removal to a place where ample fresh air is available should be followed by a warm sponge bath. Coffee may be given as a stimulant but no alcohol. Blood transfusion and injectipn into the blood of normal saline solution to counteract thickening are sometimes necessary. I n many plants where aniline is handled as a raw material of manufacture and where workers are not exposed to it in quantity, vinegar or other weak acid in which workmen may wash their hands if aniline should be spilled upon them, prevents difficulty. Salts of aniline have practically no ability to penetrate the skin and may be easily washed off. Milk in quantity has been found effective both in preventing and to some extent in curing aniline poisoning, because there is a marked increase in resistance when the stomach is full, and a large amount of liquid hastens elimination of the poison through the kidneys. Poisoning similar to that by aniline is produced by nitrobenzene, dinitrobenzene, nitroanilines, etc. Nitrobenzene is decidedly less toxic than aniline, but dinitrobenzene and the nitroanilines are more so. The latter, however, because of their lower vapor pressures, do not produce symptoms so quickly as aniline nor do the symptoms disappear so quickly. They act much like cumulative poison, in the sense that small doses reduce resistance to subsequent small doses until a point is reached where a collapse may be caused by even a slight dose. Cleanliness is the only real preventive and fresh air and rest the only restoratives. After collapse a rest of a week or more with proper food and plenty of fresh air is necessary to permit the body to void all traces of these poisons and to bring the worker back to a sufficiently healthy condition to continue work. All traces of cyanosis should have disappeared before permitting reexposure. Prevention of Poisoning The prevention of these types of poisoning is strictly a problem for the plant engineer in designing the plant and of the plant superintendent in enforcing cleanliness. THE ENGINEER’S PROBLEM--Waste of material through faulty equipment is insignificant compared with the waste of man power which it occasions. Apparatus in which these dangerous materials are handled must be so built and so vented that no leakage of vapors or steam can occur in the working spaces. This cannot be stated too often for safety. Wherever possible, such apparatus should be operated under a very slight vacuum-a few inches of water will suffice-and the vacuum pump or aspirator should be vented to the air a t a safe height above the plant. Ventilation is not given sufficient consideratioii in most plants. The ideal plant for conducting such operations would have a high roof made up entirely of louvers and no walls. Such conditions cannot be realized in practice, however, but they should be approached as closely as possible. Louvers and removable roofs may be provided and walls should be set back to allow eight or ten feet of free space between apparatus and walls, as well as between apparatus and roofs. ventilation should be provided when it is necessary to keep the roof on and the plant doors and windows closed. Some engineers insist that ventilating air should be cold, as this prevents the vaporization of the dangerous materials and causes the condensation of any that may have been vaporized. Others insist that the excess clothing men are forced to wear reduces their efficiency and that forcing vapors to condense rehults in
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unnecessary poisoning. Consequently, they contend that ventilation should be by warm air and that employees should wear as little clothing as is compatible with their comfort. However, all are agreed upon the necessity of providing forced ventilation and hoods over apparatus that may have to be opened. A further point for the earnest consideration of the plant engineer is the provision of grating floors to prevent spilled material coming into contact with the shoes of workers. Cement floors should be covered by gratings, and well drained beneath so that no accumulation of material may cause trouble. THE ~CPERISTEKDEST’SREsPossIBILITY-The plant superintendent has the greater responsibility in preventing sickness among his employees. His first care should be to prohibit any employee from working when he has recently taken alcohol in any form and to see that all employees are cautioned against its use a t any time. It has frequently been found that a victim of severe poisoning has recently partaken more or less freely of some alcoholic beverage. A single drink of whiskey will increase a man’s sensitivity to these poisons by several hundred per cent. The superintendent should see that any man who shows signs of cyanosis is removed from danger immediately, and that anyone upon whose clothing or shoes poisons are spilled is a t once required t o bathe, and put on clean garments. Prevention to be effective must be immediate. Bn hour after an accident may be too late. Plant walls must be carefully washed a t frequent intervals-not more than a week should be permitted to elapse between washings-and floors should be washed every time anything is spilled on them. Assistance from the maintenance department should be sought immediately when any leaks are noted. The superintendent must also insist that his men bathe completely and change all their clothing before leaving the plant a t the end of their shifts. This rule is particularly difficult to enforce on the foreigners, as is that against the use of alcohol. I n many plants the rule requiring baths can be enforced only by providing changes of underwear and, in some cases, other clothing for the use of workers; yet even then i t has been found profitable. First Aid The first-aid department need be little concerned about poisoning if these provisions of the engineer and superintendent are properly enforced. This department should provide warm, well-ventilated rooms where patients may be allowed to recuperate, and supervise the enforcement of cleanliness rules. Periodical examinations of the blood of workers to determine their physical state should be carried out, and rest away from poisons or transfer to other departments of the plant recommended for those !Those blood condition is serious. Hot coffee and milk should be always readily available for serious cases. The poisons under discussion are essentially blood poisons, and their effects are too closely dependent upon personal idiosyncrasies to permit more accurate description or more exact prevention or cure. During the mar period, it developed early that women were eqpecially subject to such poisons and should not under any circumstances be permitted to engage regularly in occupations involving such exposure. A theory was also developed that the darker one’s complesion, and hence the thicker one’s skin, the less susceptible one would be to such poisons. It mas noticed that negroes and the dark peoples of Southern Europe were generally less affected than the light S o r t h Europeans. That is only a rough approximation, however, and there are as many exceptions as there are cases which fit, as subsequent experience has shown.
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I S D U S T R I A L A N D ENGINEERIVG CHE.1.IISTRY S k i n Affections
The difficulties treated have involved actual blood poisoning, but another type of poisoning occurs in the organic industries which may be equally serious. Various compounds produce severe skin eruptions. Typical of these are nitrosodimethylaniline, the azo dyes generally, crude anthracene, and most dangerous of all, the chloronitrobenzene derivatives. Dust from any of these compounds irritates the skin to the point where violent scratching results in the formation of small and very painful boils. I n severe cases this trouble may become extremely dangerous from the possibility of gangrene and septicemia following too violent scratching. I n the case of the last-mentioned compounds both vesicant and poisonous properties are noted, and especial care must be taken with them to prevent exposure. These itches are very little understood even yet, and it is customary throughout the industries in which they are met to consider them entirely as matters of personal idiosyncrasy. One frequently hears statements that such and such a man cannot even enter plants where he may be exposed to these compounds without becoming seriously affected. On the other hand, there are men who have been continuously exposed to them for months without feeling the slightest discomfort . No rules other than cleanliness have been devised for preventing this type of poisoning. Operations in which these materials enter should be conducted in such a way as to avoid dusting, walls should be frequently washed and running water should be provided for washing off any dust which may get on the employees. As a rule gloves should not be used, as they may become filled with the dust and promote trouble by holding it in contact with the skin. The eruptions generally appear on the hands and wrists as well as upon the neck and face. Hats should be worn to prevent the accumulation of dust in the hair-although there is a superstition that such materials promote the growth of hair! Avoidance of contact with these materials by those who have natural idiosyncrasies against them and care to prevent contact even by those who are not particularly susceptible has resulted in the practical elimination of this trouble. Baths a t the end of shifts and changes of clothing before leaving the plant cannot be recommended too strongly. I n serious cases salves may be applied to reduce the itching after the parts have been bathed in alcohol t o remove as far as possible traces of the poisons. General Observations
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-4few statements in the literature regarding compounds which cause these various types of poisoning deserve correction. In general, the introduction of methyl or ethyl groups into the benzene ring or into a side chain materially reduces the toxicity of a compound. Toluene and xylene, although still somewhat toxic, are much less so than benzene itself. Aniline is much more poisonous than either toluidine or xylidine. I n fact, workers in aniline usually consider the latter compounds almost harmless. In the same way dimethylaniline has no noticeable effect upon workers in it, but they avoid exposure to fumes of methanol used in its manufacture. Diethylaniline is similarly inactive. However, the introduction of a nitroso group into either of the last two compounds brings about serious difficulty by introducing irritant properties. Among the nitro compounds, the introduction of a second nitro group appears to have a very marked effect in increasing poisonous properties, particularly if it is in the meta position to the first. This is true of the introduction of an amino
Vol. 17,
KO.8
group into a nitro compound or into an amino body. The meta positions appear to be most toxic in di-substituted compounds. The introduction of a third nitro group again reduces toxicity. Nitrobenzene in the literature has been given a very bad reputation which it does not seem to deserve, a t least in so great a degree, whereas the poisonous properties of dinitrobenzene seem to be greater than are described. It is probable that writers on these subjects have confused the two. Where the poisonous properties of a compound are due essentially to an amino group, the formation of a salt of the compound-hydrochloride, for instancematerially reduces, if it does not actually remove, poisonous properties. This is true of aniline and of the diamines. Where both nitro and amino groups are present, toxicity is greatly reduced on the formation of salts, probably because of the reduction in vapor pressure, but not entirely removed. In general, the toxicity of a compound of the cyanotic type is more or less directly proportional to its vapor pressure. lMuch information concerning such poisoning as has been described is available to the medical profession, but the preventive measures have not received so much attention from plant operatives until severe cases have brought the matter forcibly to their attention. The prime essential is cleanliness, both of plant and of employees. The exclusion of alcohol and of employees who show tendencies toward organic diseases of the heart, lungs, or kidneys, hemorrhage, or anemia, from operations in which exposure might result is essential. Careful followup of absences by one familiar with the symptoms produced by this type of poisoning is a valuable aid. Warnings to employees and frequent medical examinations, followed by transfers to less toxic surroundings in different departments, where such examinations justify it, must be practiced for the safety of all concerned. A physician in attendance or certainly on call a t any moment must be provided to care for serious accidents.
The Alcohol Family Reports reaching us from abroad indicate that various members of the alcohol family may command our attention for some little time, and their synthesis constitutes the most important industrial chemical development in the near future. It is rumored that a French concern expects soon to be able to offer synthetic ethyl alcohol a t a price below that of alcohol produced by fermentation. It is stated that from 13 to 19 kg. of ethyl alcohol are produced for each ton of coal carbonized, which is considerably better than the quantity of benzene recoverable from cokeoven gases. This is largely discounted by some experts who maintain that no one has as yet produced synthetic ethyl alcohol on anything like a commercial basis. A German patent, No. 350,048, and its amendment 362,537, discusses a procedure for the manufacture of synthetic butyl alcohol. Copper is used as catalyst, being precipitated from its salt solutions and then reduced a t low temperatures. German patent 384,351 of March 21,1922, indicates a number of examples, of which we give two. Neutral crude aldol is led, by means of a current of hot excess hydrogen, over a copper catalyst heated to 200" C. obtained by a reduction of precipitated copper hydroxide a t from 200' to 250' C. Two hundred parts of crude aldol, with about 150 parts of pure aldol, yield about 100 parts of normal primary butyl alcohol. Some acetaldehyde present in the crude aldol is carried over a t the same time in ethyl alcohol, which can be separated from the butyl alcohol by rectification. Another example, croton aldehyde, is led with excess steam over a copper catalyst a t a temperature of about 180" C. I n this case 200 parts yield 200 parts of butyl alcohol. Isopropyl alcohol is being produced synthetically by the Badische, and attention is still centered on plans for the increased production of synthetic methanol in Germany and in France. In many laboratories in America research has been undertaken on a serious basis which may soon be expected to lead to encouraging results and place America in a favorable world position.
