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WORLD HEALTH ORGANIZAT.ION

Geneva, 6-12 August 1963 .

ORGANISATION

MONDIALE DE LA SANTE

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^AP

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5 August 1963.

ENGLIS~ QNLY ('TT fNSL!lTION)

ASPECTS OF AIR POLLUTION BY MOTOR VEHICLES

by

Professor F. L. Petrilli and Dr

s.

Kanitz

Every motor vehicle pollutes the atmosphere in four different ways depending on whether it is:

(1)

^idling;

(2) accelerating;

(3) decelerating;

(4)

^cruising.

The volume of exhaust gas and the concentrations of the individual pollutants vary widely in.each phase. The total volume of exhaust gas varies from a minimum

of 150-190 per minute (idli~) to a maximum of more than 6000 per minute (accelerating).

It is therefore very difficult to determine the average amount of pollution caused by a motor vehicle.

The pollutants in the exhaust gases are essentially hydrocarbons, nitrogen oxides, carbon monoxide, aldehydes, etc. The respective concentrations depend upon operating conditions, e:g. the amotint of hydrocarbons released increases

greatly during deceleration, even though it is already very high during acceleration, in view·of the great volume of gases discharged during deceleration; for nitrogen oxides it is the reverse: it is during acceleration that the discharge reaches the maximum.

·The composition of exhaust gases depends also upon many other factors; e.g.

air/fuel ration, compression ratio, composition of fuel, age and maintenance of engine1 etc. In gasoline engines, for complete combustion, the air/fuel ratio should not be below 15:1. Since, however, the ratio is normally about · 12.5:1, the exhau5t gases contain products of incomplete combustion as well as

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raw gasoline. Air pollution from motor vehicles derives not only from gases discharged through the exhaust pipe but also from gases, which, blowing past the piston rings, escape from the crankcase by means of a road draug:qt tub~. _("b~c;>~~Y.");

these represent about 20-40 per cent. of total emissions. During the warm season, evaporation from the fuel-tank and from the carburettor must also be considered.

Besides gasoline engines, there are the diesel engines which are coming to be more frequently employed in small and medium-sized vehicles, creating an air pollution problem with other characteristics. Diesel engines discharge smaller quantities of hydrocarbons, but large amounts of nitrogen oxides and, in addition, black smoke, especially under heavy load conditions.

Knowledge of fuel composition is very important in the study of air pollution caused by motor vehicles. Gasoline is a mixture of several hundreds of olefins, naphthalenes, paraffins and aromatic hydrocarbons. The relative proportions vary according to the origin of the petroleum but can be modified during the refining process and the blending of the different components. The presence of one or another type of hydrocarbon is especially important during deceleration, when the quantity of unused fuel in the exhaust reaches its maximum.

Gasoline contains many additives - principally the anti-knock compounds, at first (until 1959) only tetraethyl-lead (TEL), later also tetramethyl-lead (TEM) and some others. Together with the lead anti-knock compounds, some other substances are added to prevent the deposit of lead oxides on engine valves and sparking-plugs, and also anti-oxidants, detergents, lubricants, dyes, etc.

Another aspect which is not always taken into account in air pollution from motor traffic, but_which is certainly very important, is the human factor, i.e. the behaviour of the driver at the wheel.

Having listed the various types ~f air pollution produced by motor traffic, the problem created by their interactions in the atmosphere should also be considered.

The present studies on this subject are based on observation of air pollution phenomena in Los Angeles where, industrial sources of pollution having been eliminated, the

typical "smog" was shown to be caused by automobile exhaust gases.

· "-. AP/19 page

3

The most popular theory today on smog formation (Haagen-Smith) is that ultra- violet radiations act on sulfur dioxide, nitrogen oxides and aldehydes, which react with molecular oxygen to produce atomic oxygen. The quantity of atomic oxygen

produced by the photochemical reactions of sulfur dioxide and aldehydes is limi-ted, since the reactions are irreversible. On the other hand, the absorption of u1tra- violet radiations by nitrogen oxides leads to the rupture of the nitrogen-oxygen bond with formation of ozone and regeneration of nitrogen dioxide. This latter is again available for a repetition of the process, unless it reacts with other compounds which could be present in the air (e.g. organic substances). In this case compounds are formed which could cause eye and throat irritation, damage to crops, etc.

The ozone formed during ¹¹smog¹¹ periods was found to be responsible for the deterioration of rubber observed in Los- Angeie·s .· As "to the role e-r· the various · ··

hydrocarbons in the afore-mentioned reactions, the olefins are most important, the aromatics moderately important, and the paraffins least important.

As regards the establishment of maximum allowable concentrations of pollutants produced by motor traffie, the difficulty -is the lack .. of scient.ific. pvog.f. (y;rith tpe exception of some dramatic occasions) of the har~ to health caused by such pollution.

However, if "human health¹¹ is to be considered as a state of complete physical, mental and social well-being and not mere absence of disease, as stated in the WHO Constitution, then air pollution is evidently linked to health.

Again, the most practical scientific information on the possibility of establishing air quality standards comes from California (Los Angeles) where, as already mentioned, air pollution by motor traffic is pararr.ount. A group of scientists, technologists and biologists, taking into consideration all the direct and indirect effects of air pollution on man, have established in this particular case, thr~e levels of air po1lution.

1. Adverse level ·

This is characterized by disagreeable sensations (or discomfort), e.g. irritation of the mucosa (notably of the eyes), damage to vegetation and buildin~s, reduction of visibility, etc.

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4

2. Serious level

This is characterized by changes in 'physiological functions in particularly sensitive groups of the exposed population.

3.

Emergency level

Here, the degree of pollution and the meteorological factors constitute an immediate danger.for the whole of the exposed population.

The concentrations of individual pollutants corresponding to these three levels are as follows:

I II III

Carbon monoxide lOO p.p.m. 200 p.p.m. 300 p.p.m.

Nitrogen oxides 3 p.p.m. 5 p.p.m. 10 p.p.m.

Sulfur dioxide 3 ^p.p.m. 5 p.p.m. 10 p.p.m.

Ozone 0.5 p.p.m. l p.p.m. 1.5 p.p.m.

Even though these levels refer to a particular area and are not based on the results of epidemiological research, they are very interesting and could lend them- selves to modification in the light of research conducted by others.

The problem of the true relationship between air pollution and health is still unsolved, though much research has been and is being carried out in many different countries.

First in this field were the English who, adopting an epidemiological and

clinical approach, clarified the causal relationship in their country between "chronic bronchitis" and air pollution. Later on, other countries worked on this problem.

With respect to Italy, we would recall that already in

1957,

at the Milan Conference on the Public Health Problems of Air Pollution in Europe, one·paper was devoted to first findings in some epidemiological surveys of the relationship between air pollution and pulmonary disease (bronchitis and lung cancer). The statistical analysis, which took into consideration all probable factors (socio-economic

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5

conditions, industrialization, smoking habits, ~tc.) led to some conclusions which were in some respects comparable with those of the English investigators; in others, however, (e.g. in relation to chronic bronchitis) the situation differed remarkably

from the English one. . . --·-· _ ...

With reference to the specific effects on health of air pollution from motor traffic, the research work on this subject already carried out and still continuing in the United States of America is the most important, and it may be interesting to summarize briefly its salient points.

The first group of studies concerns the effects of exhaust gases in toto.

gas~s, when irradiated with artificial sunlight, produced the same effects as the

"smog¹¹ of Los Angeles (Stephens), i.e. ozone formation, irritation of the mucosa, damage to vegetation, reduction of visibility, etc.

These

Using this possibility of producing artificial "smog", many studies were undertaken to determine the reactions of vegetation, animals and where possible of man, to various concentrations. A great deal of research is still continuing and on the basis of the findings so far, it can be said that irradiated exhaust gases contain some phyto-

toxicants whose action on vegetation is hardly distinguishable from that of "smog"

and "ozone" (Haagen-Smith); the variation in the damage is probably due to the presence of different phyto-toxicants. The amount of damage depends upon the type of fuel, the hydrocarbon/nitrogen oxides ratio, the extent of irradiation of exhaust gases, and, of course, their concentration (Brandt). Not all plants are equally sensitive and some of the variations were found also to depend upon age, meteorological factors and the amount of sunlight. In some cases it was possible to alter the sensibili::ty_ pf .. __

plants by adding chemical substances to the soil or to the leaves (Brandt). It seems very probable that phyto-toxicants alter the distribution of the soluble amino-acids in leaf tissue.

For the in vivo experiments the studies were made over shorter or longer periods

(usir~, of course, different concentrations of pollutants). Also, for the purpose of revealing effects not otherwise detectable, studies were made with concentrations much higher than those usually found in the atmosphere. An important factor which emerged

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from experimental \~ork on animals was the difference in the effects of exhaust gases, according to whether they were irradiated or not by artificial sunlight. Pattle obtained some very interesting results with a single-cylinder diesel eng~ne: he observed caeteris paribus a relationship between the mortality of _exposed animals and the air/fuel ratio and engine operating conditions. He also observed that the effects were not proportionate to the amount of carbon monoxide present in the gases.

Murphy and his eo-workers m~de and are still making some more thorough experiments.

They observed modifications in the pulmona~J func~ions of animals exposed to a mixture of pollutants a little more concentrated than Los Angeles "smog". They observed also a higher rate of carcoxyh::..emoglobinaemia in animals treated with irradiated gases than in those treated with non-irradiated gases. Also, animals with induced pulmonary oedema were shown to be more sensitive to exhaust gases.

Studies of fauna in polluted areas did not reveal any particular ~ffects, even when particularly sensitive techniques were used.

We should like now to mention the effect of the individual pollut~ts produced by motor traffic on living organisms.

Aldehydes

The aldehydes and derivates are the most irritating substances among those present in exhaust gases; on the other hand these compounds are often found as industrial pollutants. Their chief effect is on the mucosa (Sim 8: Pattle) and in sensitive subjects it is possible to detect a cutaneous hypersensitivity.

Carbon monoxide

It is generally agreed that chronic carbon monoxide poisoning does not exist, but that cases of so-called chronic poisoning are either repeated episodes of sub- acute poisoning or the sequelae of severe acute poisoning (Lindgren). ·The absence

of any appreciable symptoms after prolonged exposure to low carbon monoxide concentration~

(44

p.p.m. for 72 d~ys) in men in nuclear submarines appears to confirm this opinion (Schul te). It is also necessary to bear in mind the possibility of synergism between

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carbon monoxide and other pollutants ( sulfur dioxide and nitrogen oxide- ete·.) and- · ·-- · the modification of sensitivity in smokers and chronically exposed persons (Hackney et al., Rindgold et al.). The results of our-investigations on drivers, smokers, traffic policemen and pedestrians were negative: we could find no correlation in exposed persons between the carbon monoxide content of the air and blood levels and symptoms. These results accord with those of Sievers, Hofreuter, Clayton et al.

Carcinogens

Benz-pyrene and other polycyclic carcinogenic hydrocarbons have bB~n·faund in- motor-vehicle exhausts. The discharge is at a maximum during deceleration. It is very interesting to note that for the same amount of "tar", exhaust gases contain twice the amount of potentially carcinogenic hydrocarbons than cigarette smoke condensate (Wynder

&

Hoffman). It is also worth mentioning here that Begemarm considers traffic pollutants to be responsible for about 10 per cent. of the total carcinogenic pollutants in city air.

Lead

Lead is a well-known and ubiquitous poison and it is a normal trace element of almost all foods. The anti-knock agents added to gasoline are responsible for the presence of inorganic lead salts in exhaust gases. The health problem caused by this use of organic lead compounds became manifest when, a short time after the adoption of this process (1923), a significant number of cases of serious poisoning occurred among those haridling the pure substance and preparing the mixture to be added to the gasoline (ethylfluid). However, some years later two commissions, one in the United States and one in the United Kingdom, reached practically the srune conclusion to the effect that although caution was necessary owing to the toxicity of the substances in question there was no reason to prohibit the use of ethylfluid at the concentrations normally employed. However, the great increase in motor traffic during the last few decades has made the experts turn their attention to the potential risk J_I}_voly~_d_.~n

the inhalation of exhaust gases in large cities. The multiplication of studies of air pollution along the main traffic routes since 1945 has been accompanied by a search for evidence of lead pollution.

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Nitrogen oxides

The group of nitrogen oxides present in exhaust gases includes diffe~nt compounds with varying degrees of toxicity for man. Complex interactions occur between·t~~

different-oxides and they also contribute to the photo-chemical production of irritating compounds such as aldehydes in the atmosphere (Rogers et al.) It is very difficult to determine the true toxicity of nitrogen-oxide mixtures in the air although the.effects of individual oxides on man are already well known.

Ozone and oxidants

Ozone is o.sually considered as an index of the oxidants proQ.uced by motor traffic.

Studies have been carried out"in large towns with intense traffic to study the concentra- tions and effects of these substances (Cholak et al., Mills). It is interesting to note that ozone concentrations in European towns, particularly Paris, are far weaker than in towns in the United States. This may be due (Vassy) to the concomitant smaller concentrations of nitrogen oxides owing to the lower horsepower and lower gasoline consumption of European cars.

From the above it will be seen that the whole problem of air pollution by motor traffic is extremely complicated, both on account of the increase in the sources of pollution and of the presence of many groups of different pollutants with heterogeneous chemical and toxicological characteristics.

Apart from the general assessment of individual pollutants mentioned above, we in Genoa have concerned ourselves with two particular problems:

(1) carbon monoxide;

(2) the presence of lead in the atmosphere due to the addition of anti-knock products to gasoline.

Some brief reference to these problems may be useful.

Carbon monoxide

Apart from routine measurement ope.rations along the arterial roads in Genoa,

which have led us to some conclusions about the relation of carbon monoxide concentration to traffic conditions and meteorological factors affecti'ng dispersion, we have studied another problem which is rather important in our area, i.e. that of the accumulation

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of exhaust gases and carbon monoxide in particular beneath tunnels and arcades in both urban and extra-urban areas. The results are ~eally impressive: under some tunnels, at peak hours, the concentrations measured were close to those which can have a dangerous effect on human health

(300-500

p.p.m.). To remedy this dangerous state of affairs, it was· necessary in some cases to adopt control measures as, for instance, one-way traffic ·and additional ventilation equ~pment which, until a few years ago, would have seemed excessive.

Tetraethyl-lead (TEL) and Tetramethyl-lead (TEM)

From

1955

to

1962

concentrations of lead ranging from

0

to

20

micrograms/m

3

could be found in the air in different areas of Genoa. As stated above, interest in the problem of lead in the air was renewed recently when TEM was introduced into gasoline instead of TEL. In theory, the most disquieting feature of TEM is its higher volatility in comparison with TEL.

In order to evaluate the potential risk run by service-station operators, consumers and town populations as a consequence of gasoline containing TEM, the following research was carried out at our Institute (some of our conclusions were made known at Stuttgart in

1962,

at a VDI meeting):

1. Measurement of lead contamination in the air and on the ground near four service stations.

2. Measurement of lead contamination in the air in a confined area following refuelling of vehicles with g~soline containing TEL' and TEM.

3.

Study of acute TEM toxicity in control animals.

4.

Study of chronic TEM toxicity in control animals.

5.

Determination of lead concentration in the urine and blood of subjects exposed to air polluted by gasoline additives.

Our conclusions were as follows:

1. There is no difference in the concentration of lead in the air or on the ground whether the additive be TEM or TEL. The data provided by research'near large service

stations for nearly a year clearly confirm this.

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2. The discharges from the exhaust pipes of vehicles of different horsepower and technical construction after running the engines at the same number of r.p.m., did not differ substantially (except for logical horsepower variation).

3·

Tests for acute toxicity made on various laboratory animals substantially proved that there is no difference between the -:,wo e:ompou..'l.ds, md it cannot be said that TEM is more dangerous than TEL. The tests show that TEM may in fact be considered less toxic on the basis of the L0

50 ^results~ that is to say, the dose necessary to cause the death of half the laboratory animals treated with the toxic substance.

4.

As regards the toxic phenomena resulting from inhalation over a long period of time of minimum concentrations of TEM and TEL, although no conclusions can yet be drawn owing to the long time required for the experiment and the complexity of the research work, we nevertheless have the well-founded impression that, here again, it cannot be said that gasoline containing TEfv'l is more dangerous than that containing TEL. It is-also interesting to note that even as regards the effects on various organs and functions of the body, no difference has yet been proved between the two toxic substances.

5.

The results of the tests for the determination of lead in the blood and urine of subjects in contact with the two types of gasoline additive over a long period of time appear to confirm the findings mentioned above: the levels were found to be within normal limits.

In addition to measuring carbon monoxide and lead in the air WG also measured ozones, nitrogen oxides and hydrocarbons in different parts of the town. All results collected to date may be swmnarized by saying that the concentrations found in aenoa are, fortunately, greatly inferior to thos€ found by research workers in other large towns.

The correlation between human health and air pollution from motor traffic is naturally receiving great attention in our Institute and some of the first results have been published. Among the various studies we are making we would draw special attention to, for example, those relating to professional drivers and town traffic policemen.

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The mortality from cancer of the lungs among drivers was shown to be significantly higher than for other groups of persons of almost the same age and living conditions.

On

the

contrary~ the results of a similar survey among traffic policemen in Genoa were negative.

Some other studies on the frequency of respiratory disease show that the morbidity rates for pharyngitis1 tonsillitis and bronchitis were significantly higher in policemen who had been in the service for more than 15 years, while no difference was found with respect to influenza1 pneumonia and other diseases.

On the subject of the prevention of air pollution from motor traffic, we

should like to recall here the principles and recommendations which the more important car manufacturers have adopted and which Chandler recently put forward again:

(1) The automobile industry recognizes and accepts its responsibilities concerning the role of motor vehicles in air pollution.

(2). The automobile industry will apply pollution control measures when such measures have been proved to be effective, economically feasible and necessary.

(3) The automobile industry offers its continued assistance to all agencies concerned with the air pollution problem.

(4) The automobile industry suggests that study of the following points should be developed:

(a) evaluation of existing pollution;

(b) careful determination of sources of pollution and evaluation of their respective contributions;

(c) establishment of standards with regard to devices for the prevention of pollution;

(d) creation of bodies responsible for control and surveillance.

As far as we know1 the Italian automobile indust~J agrees with these principles and recommendations and for this reason some Italian cars are already fitted with apparatus designed to recirculate blowby gases.

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We also know that the Italian automobile industry is studying carefully the possibility of reducing the emission of carbon monoxide and of the products of

incomplete combustion, and of improving~ as far as possible~ the combustion process.

In regard to diesel motors, efforts are being made to reduce to a minimum· the emission of the typical and irritant black smoke.

Conclusions

Air pollution from motor traffic is giving rise to more and more anxiety today in Italy, especially on account of its ever-increasing volume in a country where streets are often particularly narrow.

We feel that every encouragement must be given to efforts directed at limiting or modifying the emission of air pollutants by motor traffic.

In our view it would be particularly useful if this meeting could put forward a recommendation for the promotion and co-ordination of studies and research on the control of air pollution from motor vehicles in the light of the results so far achieved and bearing in mind that progress can only be made along the lines of complete international co-operation.