By Prof. P. A. SIMPSON, M. A., M. D.

POISON IN THE AIR WE BREATHE.

There are few words in the English language which produce a more painful impression upon the popular mind than does the word Poison, and there are at least two valid reasons why it should be so. In the first place we find poison waging war against human life, sometimes openly, sometimes insidiously, often successfully; and in the second place, from remote ages down to the present day, we are accustomed to see poison going hand in hand with crime as its chief companion. But we must remember that poison is by no means an evil-doer, only as the agent of the assassin or of the suicide. These are doubtless its most hideous aspects, but there are many others where its effects are produced as surely, though often very insidiously, without any evil intention, and, like a wolf in sheep’s clothing, clad in garments which are intended for our good. It is to such cases that we wish to direct attention, by pointing out a few of the modes in our every-day life in which poison may enter the human body without our knowledge, and wherein its presence is unnoticed until disease or death makes it manifest.

Let us, then, consider in the first place the composition of atmospheric air, and how it may become so vitiated that, instead of supporting life and health, it may carry disease or death to those who breathe it. It was long thought that air was spiritual, that it was like the life, and that it was the soul of the world; but we now know that it is just as material as a piece of iron, and that it will weigh down the scales of a balance in the same way; and the time may yet come when by means of immense pressure and intense cold it may be condensed into a liquid, as carbonic acid and other gases have already been. We find air present everywhere. There is scarcely a solid, however compact it may appear, which does not contain pores, and these pores are filled with air. It is to be found in abundance in the soil; indeed were it not so, numberless worms and insects which inhabit the latter would cease to exist. The most compact mortar and walls are penetrated by it, and water in its natural state contains a large quantity of air in solution. The atmosphere was formerly believed to extend no higher than five miles above the earth’s surface, but meteorological observations have since shown that it extends to a height of more than two hundred miles. Owing to the force of gravity the air is much denser near the earth, and gets thinner, layer by layer, as you ascend. If then the atmosphere were possessed of color it would be very dark just round the globe, and the tint would gradually fade into space. There is no absolutely normal condition of the air we breathe; or, if there be, it is not at present known. It contains, however, in all cases, unless under purely artificial conditions, two essential elements, which are nearly invariable under normal circumstances, namely, oxygen and nitrogen, and two accessory elements which vary extremely in amount, but are practically never absent, namely, carbonic acid and water. Without either of the first two, air could not exist, and without the last two, air is scarcely found in nature. Their combination moreover is not a chemical union but a simple mechanical mixture. But besides these constituents the air contains an immense amount of life, and small particles derived from the whole creation. In the air may be found animalcules, spores, seeds, cells of all kinds, eggs of insects, fungi and elements of contagion, besides formless dust, and sandy and other particles of local origin. For example, no one can travel in a railway carriage without being surrounded by dust, a large portion of which may be attracted by a magnet, consisting as it does in a great measure of minute particles of iron derived from the rails. The purest air has some dust in it. There probably never fell a beam of light from the sun since the world was made which would not have shown countless numbers of solid particles. Roughly speaking, 100 measures of air, if pure, should contain 78.98 parts of nitrogen, 20.99 of oxygen, and .03 of carbonic acid. Without oxygen a candle will not burn, and animals can not live; but for the purposes of animal life this gas requires to be diluted, and this is effected in the atmosphere by a large admixture of nitrogen. In fact, nitrogen seems to act in the animal economy purely as a diluent or vehicle for the administration of oxygen. Carbonic acid, as far as we know, is not essential to the animal kingdom. To man it is simply a superfluous ingredient, but harmless when in small quantity; to the vegetable world, on the contrary, it is a food which together with water often suffices to support the entire life of a plant. When, however, from any cause the quantity of carbonic acid is much increased, it becomes highly poisonous to man. When the amount reaches 10 or even 5 volumes per cent. it produces fatal results, and even 2 per cent. occasions in most persons severe headache. The balance between carbonic acid and oxygen in the atmosphere, continually disturbed in one direction by the animal kingdom, is constantly maintained by the vegetable kingdom; for while the former consumes oxygen and gives off carbonic acid, the latter for the most part performs the opposite function. Owing to certain local conditions, however, which we shall presently consider, the quantity of oxygen in the atmosphere sometimes falls below the normal amount to the extent of over 3 per cent., while the carbonic acid proportionately increases. In order to estimate the importance of what might otherwise appear trifling differences in the composition of the air we breathe, we must remember that we take into our lungs from 1,000 to 2,000 gallons of air daily. Now the presence of only a few grains of impurity in a gallon of water would render it unfit for drinking purposes, although as we only drink a comparatively small quantity of water the whole of these few grains would not be swallowed in a single day.

We have spoken of carbonic acid as an impurity in the atmosphere; and so it is, for it is unfitted to support animal life. An animal will die from suffocation in an atmosphere containing plenty of free oxygen if it contains over 10 or 12 per cent. of carbonic acid gas. But a minute increase of this gas in the atmosphere is of most importance from the fact that it always comes in bad company, and is found to be a measure of the many impurities which accompany it. Moreover, for every increase of carbonic acid there is a corresponding decrease in oxygen, so that we have in such cases a double effect, viz., a subtraction of the life-giving principle of the air, and the addition of noxious substitutes. These noxious substitutes consist for the most part of organic matter, either of animal or vegetable origin. The exact nature of the organic substances, which constitute the specific poisons of contagious diseases, still remains obscure. Whether they consist of inconceivably minute particles of decaying matter, or of living microscopic germs; whether in some instances they are conveyed by particles of skin and pus-cells from the diseased to the healthy, or are condensed with the watery vapor of the atmosphere and thus disseminated; all these are questions which have yet to be satisfactorily answered. It is, however, certain that almost invariably the atmosphere is made the vehicle of the contagion or deadly agent, whatever may be its nature; and hence the great importance of taking such precautions as will prevent the contamination of the air; or at all events, aid in dissipating or destroying its more hurtful impurities. An estimate of the amount of organic impurity in the air of our large cities may be formed by considering the enormous quantities of carbonic acid gas that are daily and hourly poured forth in these industrial centers. Dr. Angus Smith, whose investigations regarding “Air and Rain” have won for him a world-wide celebrity, has found that in the city of Manchester 15,066 tons of carbonic acid are daily passed into the air that envelops it; and Dr. de Chanmont states that 822,000,000 cubic feet of this gas are generated in London per day, or more than 9,500 cubic feet per second. Fortunately the operations of nature are in themselves calculated to restore a state of equilibrium in the constitution of the air. Injurious gases become diffused, diluted, or decomposed; animal emanations are absorbed in the processes of vegetation; suspended matters are washed down by rain, or fall by their own weight, while many organic substances are so acted on by oxygen as to render them innocuous. Thus the vast aerial sea maintains a uniformity of composition, owing to the mighty forces of nature, without which all our sanitary measures would be futile. But if nature be so powerful as a sanitary agent, how is it that we still require to cope with that formidable enemy which we call foul air? It is because we ourselves are constantly vitiating the atmosphere around us whether we live, or work, or die, and because the impure products thus generated are not sufficiently provided against by efficient ventilation. Let us glance briefly at the principal sources from which these impurities rise. These may be grouped under three heads, viz.: (1) Respiration; (2) Putrefaction; (3) Trades and Manufactures.

Respiration.—The air which we draw into our lungs with every breath contains twenty-one per cent. of oxygen, but when we expire it again it only contains 13 parts. We have, in fact, abstracted 8 per cent. of oxygen and given back in its place a poisonous mixture of carbonic acid, organic matter, and watery vapor. We breathe out this poisonous mixture at the rate of one gallon each minute, but (even apart from the organic matter) it is so impure, owing to the amount of carbonic acid which it contains, that each gallon would require to be diluted with one hundred gallons of pure air before being again fitted for respiration. In such a city as London then, the air is being polluted even by the carbonic acid which we exhale at the rate of nearly six hundred million of gallons per minute, to such an extent as to render it unfit to be breathed again. Surely this should make us welcome every strong gale as an angel sent from heaven bearing healing on its wings. But it is in dwellings, and especially in the dwellings of the poor, that the polluting effects of respiration are greatest, for in these it is too often the case that man places every possible obstacle in the way of nature’s methods of ventilation. Moreover, in apartments that are crowded it is practically impossible to maintain the air in a state of purity, and thus they become hot-beds of disease. The very interesting experiments made by Dr. Angus Smith upon himself in an air-tight leaden chamber, led him to the conclusion that, in air containing an increased amount of carbonic acid, this gas alone, even without the other hurtful ingredients, such as organic matter, rapidly produces poisonous effects—indicated by feebleness of the circulation, extreme slowness of the heart’s action, and great rapidity of the breathing—and that when men are exposed to it they are really gasping for breath, without being aware of the cause.

The presence of carbonic acid in the air we expire is readily seen by blowing our breath, by means of a tube, into a bottle containing ordinary lime-water. The water soon becomes opalescent and then milky in appearance, owing to the formation of carbonate of lime or chalk; the carbonic acid of the expired air having combined with the lime previously held in solution. It is this principle which is taken advantage of in order to estimate the amount of carbonic acid in atmospheric air. Dr. Angus Smith lays down a simple practical rule whereby any one may ascertain if the air of an apartment contains carbonic acid to a dangerous amount, viz.: “Let us keep our rooms so that the air gives no precipitate when a 10½-ounce bottle full of air is shaken with half an ounce of clear lime water.”

It is well known that speedily fatal results arise from overcrowding and want of fresh air. Out of the one hundred and forty-six prisoners confined in the “Black Hole of Calcutta,” one hundred and twenty three died in one night; and it is significant that many of the survivors afterward succumbed to “putrid fever.” Nor have similar instances been wanting in this country. Of the one hundred and fifty passengers that were shut up in the cabin of the Irish steamer Londonderry, with hatches battened down during a stormy night in 1848, seventy died before morning. In these two catastrophes suffocation was doubtless the direct cause of death, but the fact that “putrid fever” attacked many of those who were carried out alive from the “Black Hole of Calcutta,” showed that the foetid exhalations to which they were exposed must have aided largely in destroying the lives of the immediate victims. The re-breathing of foetid matter thrown off by the skin and lungs produces a kind of putrescence in the blood, in proportion to the amount inhaled, and to the period of exposure to its influences; and even air only moderately vitiated, if breathed for a long time day after day, produces most serious results. These results are seen in pale faces, loss of appetite, a lowering of the spirits, and a decrease of muscular strength. That air polluted by respiration is the one great cause of consumption, which may be handed down from parents to children for generations, rests upon such a mass of facts, that it is no longer controvertible. For instance, we know that increase of the disease occurs pari passu with an increase in the density of population; that in manufacturing centres, where the males are the chief workers at indoor employment, the male death-rate is the highest; that in others, where females are principally required at indoor work, they suffer most; and that in agricultural districts, where the men spend nearly all their lives in the open air, and the women scarcely ever leave their cottages, the female death-rate from this disease is higher than the male. Moreover, the testimony of the most able physicians at home and abroad, the results of inquiries as to the prevalence of this disease amongst the picked men of the armies and navies of the world, the reports of hospitals for consumption, and of commissioners and committees appointed to make special investigations of jails, workhouses, and schools—all these point to poisoning by impure air as the most fertile source of consumption and many allied diseases.

Putrefaction.—We now pass on to the second source of foulness of the air, viz.: putrefaction. Putrid emanations have from the earliest times been held to be capable of producing injurious effects on the human system. In the Bible we read of the great care taken to disinfect or clean vessels which may have contained any putrid matter, and in ancient Rome measures were adopted for the efficient cleansing of the sewers and streets of that city. Our present method of disposing of our refuse is by means of water, which washes it through channels called “sewers” to the sea. But meanwhile the organic portions are undergoing decay, and certain gases are thus evolved, which, mixing together, form what we term “sewer gas.” The principal gases thus given off are carbonic acid, nitrogen, and sulphuretted hydrogen, and although this mixture if breathed is injurious to health, it can not be regarded as poisonous. Thus sulphuretted hydrogen (similar to the odor given off by rotten eggs) although a deadly poison when inhaled in large quantities, is so diluted in sewer gas that its poisonous properties are in a great measure neutralized. There is still, however, sufficient sulphuretted hydrogen in sewer gas to render it very injurious by lowering the tone of health, and by gradually diminishing vitality to such an extent that disease ensues. What, however, is of far greater importance as a poisonous agent, is the organic matter which is held in suspension by these gases. The composition of this organic matter is by no means uniform. It is composed of particles from all kinds of decomposing matter, sometimes containing minute living organisms, and sometimes without doubt the germs of disease. The exact nature of these germs of disease is still a matter of uncertainty, and the question as to whether they may appear spontaneously during the progress of decay, or whether they are merely wafted by sewer gas, just as the ripe seeds of many plants are scattered by the atmosphere, is equally unsettled. This, however, has been sufficiently established, that when diseases do come amongst us they take root with most effect in those places where decomposing matter is found, and that the germs of these diseases find in the organic element of sewer gas a congenial soil, in which they can increase and multiply indefinitely, and by which they can be carried from the dead to the living. That typhoid fever depends, to a great extent, upon the polluted air of sewers, cesspools, and of the soil, is proved by very strong evidence. In some cases the disease has been confined to a particular part of the house, especially exposed to the effluvia from badly trapped drains, where there could be no doubt as to the source of the infection. The sewer air, laden with the specific poison, may be inappreciable to the senses, but its hurtful effects make themselves felt none the less, and, as recent events have shown, may sometimes exhibit themselves in the most exalted stations of life. Nay, more, it would seem that persons of the upper and middle ranks in towns are more liable to be attacked by typhoid fever than the poor classes; the reason being that the houses of the former are more generally connected with sewers, and either from structure or situation are of higher elevation, so that the light sewer gases, obeying natural laws, are more apt to accumulate in the drains of such houses, and failing efficient trapping and ventilation of the drains, to effect an entrance into the houses themselves. There is good ground for the belief that cholera, diphtheria, scarlet fever, as well as many other diseases, are occasionally spread by means of the air of sewers and cesspools; but whether these diseases originate spontaneously in this way, or whether the sewer gas only serves as a carrier of the disease-germs, is a question, as in the case of typhoid fever, as yet unsettled.

Trades and Manufactures.—Let us next consider some trades and manufactures which have an injurious influence upon persons engaged in them, and to a certain extent upon the community at large. The injurious effects are owing to solid particles and offensive gases which are given out into the air. The result of inhaling air more or less charged with solid particles may be easily explained. When the latter reach the entrance to the windpipe they at once set up irritation in the delicate lining membrane, and nature tries to repel the intruders by the involuntary cough which results. Should this fit of coughing fail in doing so, a quantity of glairy fluid is poured out from small glands in the windpipe, and this fluid enveloping the solid particles tends to prevent them from doing further mischief. Should they, however find their way lower down into the air passages, nature has provided a very beautiful mechanism for their expulsion. The entire lining membrane of these passages is covered with innumerable minute hairs, or “cilia” as they are called, which, by constantly waving in an upward direction toward the mouth, tend to carry the solid particles, and the glairy secretion which they have provoked, away from the lungs, and so out of harm’s way. This wonderful provision of nature is sufficient for the purpose, provided the strain be not too prolonged; but when the supply of irritating particles is constant, or nearly so, the nerves and muscles involved in this mechanism become exhausted and cease to perform this process of expulsion. The irritating particles are now no longer removed from the delicate membrane of the air passages upon which they lodge, this membrane becomes inflamed, and bronchitis or asthma is the result. But this inflammation, at first only affecting the superficial membrane, may sink into the deeper tissues and affect the lung itself, in which case the original attack of bronchitis frequently merges into a condition of a consumptive nature. This will explain why many trades are injurious in which the danger to health is due to the fine dust floating continually in the air of the premises. For example, the particles of coal dust in the air of mines, and the smoke from factory chimneys; particles of steel and grit given off in grinding; organic dust or fluff in shoddy and flax mills; the dust in potteries, china works, pearl button manufactories, in polishing and cement works, in brass works, in marble and steel polishing works of various sorts, especially where emery is used; in all of these cases the solid particles are inhaled and tend to produce disease in the lungs and air passages. Moreover, the severity of the effects is chiefly dependent on the amount of dust, and on the physical conditions as to angularity, roughness or smoothness of the particles, rather than on the nature of the substance, except in some specific cases. The habitual inhalation of coal dust in the air of coal mines very frequently results in consumption, and the fine divisions of the lung become so blocked up by the particles of coal that the term “black lung” has been applied to the appearance presented by the lung after death. It has been found that the death rate from consumption among miners who work in mines where the air is changed rapidly, is very much less than among miners who work in mines that are badly ventilated. Of all unhealthy occupations that of steel-grinding is the most fatal. Steel-grinding is divided into the dry, wet, and mixed methods; and the injurious effects vary according to the amount of water used on the stone. Forks, needles, etc., are ground on the dry stone, and accordingly the men and boys employed at this kind of work are found to be the greatest sufferers. Dr. Hall, of Sheffield, has furnished important information as to the average duration of life among the artisans in steel, which he found to be as follows, viz.: dry grinders of forks, 29 years; razors, 31 years; scissors, 32 years; edge-tool and wool-shears, 32 years; spring-knives, 35 years; files, 35 years; saws, 38 years; sickles, 38 years. In this and many other similarly injurious trades various methods have from time to time been devised, more especially of late years, whereby the dust might be prevented from entering the air-passages, such as fans for blowing it away, and respirators of various kinds to filter the air as it is being breathed; but it has been found that workmen themselves frequently object to any innovation which appears to them to interfere with their more immediate comfort. There are some trades where the dust given off acts not only as a mechanical irritant when breathed, but where the substance thus inhaled acts as a direct poison. For instance, manufacturers of white lead and other mineral paints frequently exhibit symptoms of poisoning in this way, and workmen who use arsenical compounds, as in the making of wall papers, artificial flowers, etc., are often the victims of poisoning by arsenic. This poisoning by means of arsenical wall papers deserves more than a passing notice, owing to the dangerous and even fatal effects which they induce, not only in the workmen who prepare them, but also in persons inhabiting apartments where the walls are covered by them. These wall papers are mostly of a beautiful green color, the latter being due to a paint composed of arsenic and copper. Owing to variations of heat and moisture the green particles are constantly being set free from the paper and carried about the room by ventilation. Some idea of the amount of poison with which so many people are surrounded in their rooms may be formed if we consider that this green pigment contains fifty-nine per cent of arsenic, and that a square foot of one of these wall papers contains on an average more than sufficient arsenic to poison twelve persons. In addition to the cases which most physicians are now so familiar with, where dangerous symptoms of poisoning have been traced to this cause, it is much to be feared that insidious and chronic disease is too often due to this practice of covering the walls of our sitting-rooms, and more especially our bedrooms, with arsenic. It may be remembered, however, that a wall paper may be green and yet not contain any arsenic, so that the following simple method of detecting an arsenical paper may be useful. If a camel-hair brush be dipped in an ordinary solution of ammonia, and applied to the green portions of the suspected paper, the green will be rapidly changed to an azure blue color if arsenic be present. Some such simple test is all the more important, because green papers, “warranted free from arsenic,” have been found to contain a large percentage of that poison.

In addition to the sources of pollution of the atmosphere which we have been considering, there are various trades and manufactures in which poisonous matters are given off. Some of these are of an organic nature, as in the melting of fats, in the making of size and glue, in the boiling of oil, in the boiling of bones, and in many other processes carried out on a considerable scale, where the emanations are highly offensive and often of unknown chemical composition. Gas works must be included in this poisonous group, owing to the accidental escape of gas, sometimes in large quantity. In lime kilns enormous volumes of carbonic acid gas are poured out, both from the limestone burnt and from the fuel employed, and in this way persons living in the immediate neighborhood have been suffocated. In chloride of lime (bleaching powder) manufactories, and in places where it is used for bleaching wool and other materials, chlorine gas is given off into the air, causing when inhaled a great amount of irritation in the air passages. Moreover, this chlorine vapor is often carried in the air for long distances. In other branches of industry the workers are exposed to the vapors of sulphurous acid and muriatic acid, both of these being very irritating, and giving rise to various diseases of the lungs and eyes.

Such, then, are a few of the impurities, more or less poisonous, to be met with in the air we breathe; and dangerous to health as all of them are, it must be admitted that they do far less mischief to the public health than the continual mismanagement of our atmospheric food, common in all classes of society, by which it is rendered unfit to support a healthy life. The two ways in which air may be rendered thus comparatively valueless are either by excluding it too much from our dwellings, and this is the fault of the rich, or by crowding too many people together in small rooms, and this is the fault of the poor. In the houses of the better classes the air is kept out by closed windows, doors, curtains, and even in some places by putting screens before the fire-places in summer, and in bedrooms in winter when fire is not used.

Pure air is, in fact, the most important of all health factors. When it is breathed freely, plentifully, and continually, there are few diseases which it will not enable the body to resist. Nay, even some injuries, which, received by the denizens of the overcrowded city, would be speedily followed by death, will be readily recovered from by the agricultural laborer or country farmer, who, always breathing a pure atmosphere, has thus stored up a great amount of additional constitutional force.—Good Words.