AN ANALYST'S VIEW OF OUR POLLUTED PLANET The analysis of our environment pollution
levels is a challenging
attracting
more analytical
in the interest of
reducing
and expanding activity that is chemists as the field
to expand. The natural skepticism
continues
of the analyst is
badly needed as numbers of all kinds tend to
proliferate,
even though standard methods are just now beginning to appear. The implications
of threshold limit values and ambient
air quality standards are of such great consequence that every analyst should be most concerned
to society
with the validity
of these numbers and their correct incorporation
into laws.
Ralph G. Smith Department of Occupational and Environmental Health School of Medicine. Wayne State University Detroit, Michigan
IT is AN OBVIOUS FEATURE of every¬ day living t h a t numbers of all kinds, and in great profusion, seem to be of concern to us, and are endlessly discussed by all news media, our political leaders, and indeed by ordinary citizens. Although m a n y of these people have almost no idea what the numbers really mean, they are rarely deterred from using them to m a k e observations on the state of our society, or to promote legislation to improve matters. Perhaps nowhere can the situation be so well illustrated as in the case of environmental pollution, where surely everyone by now has become alarmed by the quantity of something or other in our air, water, or land. An analyst should be different 24 A
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ANALYTICAL CHEMISTRY
from his fellow man, at least when dealing with numbers which he, or others like him, have brought into existence. He should, I think, be skeptical of most data, and should automatically wonder how the numbers were derived and what errors might have entered into their creation. Consider a recent example of some data which were newsworthy for a day or so. I n the spring of 1967, the statement was made in a news program for consumption by a national radio audience t h a t the average New York resident inhales about 700 -pounds of dirt in one year! To an analyst, particularly one in the field of air pollution, such a statement is an immediate challenge. Even allowing for a fair amount of inefficiency in retaining
REPORT FOR ANALYTICAL CHEMISTS "I propose, as an analyst, to take a look at the pollution that plagues our planet, and to make some observations which I believe an analyst is entitled to make, and for which he is perhaps uniquely qualified. These qualifications stem from the belief that all analysts are skeptics; or, if not, they should be. If, after years of analytical experience, a chemist doesn't in stinctively question numbers and statements concerning the composition of matter, he is surely a most unusual practitioner of our craft." this much dirt, a New Yorker would be expected to show phenomenal growth! The dirtiest urban air contains at most about a milligram of solid contaminants per cubic meter (usually expressed as a thou sand micrograms per cubic meter). A generous estimate of the amount of air inhaled by a human being per day is about 30 cubic meters—so that on a yearly basis, a New Yorker could conceivably inhale as much as 11 grams. It is probable that an average intake would be more nearly 2 grams per year, or possibly 140 grams in an average lifetime! Undoubtedly, somebody goofed in preparing the news re lease, but it is interesting to specu late on the extent to which the num ber was ever questioned by anyone. I am sure that most analysts would have experienced immediate doubts about its magnitude and started mentally checking it. The analyst's skepticism is based on his daily en counters with the uncertainties with which he must live—ordinary ana lytical uncertainties and the errors of the methods. The analyst also knows that the specificity of a method might leave something to be desired and that the sensitivity of a method can affect the validity of a value. For example, when the concentra tion of ozone in air is discussed, the analyst knows that the number was probably obtained indirectly from a property of ozone—its ability to oxidize something—and that any thing that will oxidize or reduce the reagents used will also affect the re
sult, so that the number cited might be related only by chance to the amount of ozone in air. A perfect field method for ozone has yet to be devised. Similarly, very strict limits for sulfur dioxide in the am bient air are being considered, yet most of the data in the past have been based on conductivity readings after the passage of the air through a mild oxidizing solution. Any thing that will alter the conductiv ity of water is therefore interpreted as sulfur dioxide! Nevertheless, standards are set, numbers are pro posed, and most people are reason ably unaware that analytical uncer tainties might be enormous, and in some cases be enough to make the values nearly worthless. Because world-wide concern with pollution is now a reality, and be cause many more analysts may thus be performing analyses of air and water, it seems timely to further ex amine the nature of the numbers with which we must deal. What's in a Number?
The need for large numbers, us ually for the purpose of impressing large numbers of people, is com monplace. We are all readily im pressed by estimates of pollution damage running into billions of dol lars, and are accustomed to being alarmed at the number of tons of a contaminant in our atmosphere. It is possible, however, to move a deci mal, or take a large enough area, or a long enough time period, and get almost any number desired. There
fore, some care should be taken to select appropriate units. Some thing expressed at the 0.01 per cent level does not seem like much, for example, but when expressed as a hundred parts per million, it is somewhat more alarming, and α hundred thousand parts per billion may be frightening! There is, of course, a right time to use per cent, parts per million, parts per hundred million, or parts per billion, but those who wish to promote action need only change units if they wish. For example, assuming that the area of Detroit, Michigan, is about 225 square miles, a layer of air 1000 yards thick containing carbon monoxide at a concentration of 1 ppm can be estimated to contain approximately 1000 tons of carbon monoxide. Although it may be use ful for inventory purposes to calcu late tonnages of pollutants in the atmosphere, a better appraisal of the probable effects of exposure to 1 ppm CO can probably be made by thinking of it in just such terms. As analysts and scientists we have the responsibility, I believe, to present our findings in the most cor rect form possible. Ten or twenty years ago, rather few people had much concern with air pollution, for example, either inside the workplace or outdoors, but today there is wide spread public interest. The public is alarmed; people are concerned; they want action. Hence, as might be expected, we see a great increase in legislative activity, and we have a tremendous increase in the num ber of people involved with air VOL. 40, NO. 7, JUNE 1968
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REPORT FOR ANALYTICAL CHEMISTS
studies. No doubt many chemists who led a relatively peaceful life up until now dealing with the products of their employers have been confronted with the need to do some air analyses, and to relate the results to standards of one kind or another. If so, it is probable that a sense of confusion and frustration has developed, for existing standards are usually confusing, tentative, or contradictory, while for many substances it is impossible to find anything even resembling a standard. As yet there exist relatively few ambient air standards, equally few standard methods, and only very recently National Bureau of Standards standard samples on which to test methods (see pages 75Aand 117A). Threshold Limit Values and Ambient Air Quality-Standards
It may be of interest for us to examine some of the threshold limit values that are currently used to evaluate the pollution levels of industrial air within the workplace and the ambient air quality standards that are only now coming into use for evaluating outdoor air. Threshold limit values (TLV's) are defined by the American Conference of Governmental Industrial Hygienists as follows: "The Threshold Limit Values refer to air-borne concentra-
tions of substances and represent conditions under which it is believed that nearly all workers may be repeatedly.exposed, day after day, without adverse effect. Because of wide variation in individual susceptibility, exposure of an occasional individual at or even below the threshold limit may not prevent discomfort, aggravation of a pre-existing condition, or occupational illness." By contrast, ambient air quality standards, which are presently being formulated under the provisions of the National Clean Air Act, are intended to protect property as well as health, to be applicable to the entire populace, and to recognize that air must be breathed 168 hours per week. I t is logical, therefore, that the permissible concentrations implied by the two kinds of standards may be greatly different in most cases. Figure 1 exemplifies the differences which may be encountered. The threshold limits for total particulate matter, iron oxide fume, zinc oxide fume, and particulate fluorides are compared to a proposed air quality standard for total suspended particulate matter. Uj3ing the concentration units most suitable for air quality standards, ,u;g/ms, it can be seen that the total amount of particulate matter per-
mitted in the industrial plant, when the substance involved is considered inert or relatively non-toxic, is 15,000 /ug/m3. As individual substances which are believed to be more active physiologically are encountered, the threshold limits tend to be reduced so that iron oxide, zinc oxide, and fluorides at 10,000, 5,000 and 2,500 /xg/m3 reflect increasing toxic response to these substances. The probable magnitude of an air quality standard for total particulate matter not known to be made up of toxic substances is much lower—around 100 jug/m3. Such large differences in permissible concentrations give rise to many kinds of speculation. Fundamentally, we wish to be certain that standards dealing with the same substances are consistent with one another. If 15,000 /xg/m3 can be safely tolerated by a workman throughout a working week, is it necessary that a level only 1 / 1 5 0 th as great be maintained to protect the health of the population at large? Perhaps it is, or perhaps the air quality standard is set so low for reasons other than health, or perhaps the threshold limit value should be lowered. We, as analysts, should know the bases for all standards, and be assured that sampling and analytical methods are giving the kind of information germane to them. In the case of particulate
Figure 1. Particulate matter in air—threshold limit values and air quality standards 26 A
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ANALYTICAL CHEMISTRY
REPORT FOR ANALYTICAL CHEMISTS
matter, for example, total weight (which we measure) is a rather unsophisticated property of matter, and may be relatively unimportant if visibility reduction is what we are really concerned about. For some substances, the arguments are relatively simple. In the case of such widely different metals as lead and beryllium, for example, all known limits have been suggested in order to protect human health, so they clearly should be sensibly related to each other. The present threshold limit value for lead is 200 /xg/m3 in air, and the proposed air quality standards for lead range from 1 to 20 /xg/m3. Urban air will commonly contain more than 1 /xg/m3, primarily due to the use of leaded fuel additives. Meeting a standard of 1 /xg/m3 would be extremely difficult, and would in effect probably rule out the use of leaded fuels. Aside from this enormous economic consideration, what is the rationale for believing that 1 /xg/m3 is in some way injurious to all of us, whereas 200 /xg/m3 can apparently be tolerated by 80 million working people, admittedly exposed only one fourth of a week? The ratio doesn't appear to make good sense toxicologically, and it might be assumed that 200 /xg/m3 is too high or that 1 /xg/m3 is too low. Common sense tells us that the truth probably lies somewhere between.
The extremely low threshold limit value of 2 /xg/m3 for beryllium has apparently succeeded in preventing occupational berylliosis, but evidence some years ago seemed to indicate that a much lower ambient air quality standard, 0.01 xig/m3, was required to prevent cases in the general population. Again, the ratio of 200:1 for the two limits doesn't appear to make good sense, and considerable controversy over the matter is still readily found. The analytical chemist is more involved with this controversy than most, because some confusion has arisen as a result of analyses for traces of beryllium which are of questionable accuracy at these very low levels. To compound these difficulties, there is the belief on the part of some that certain beryllium compounds are far less toxic than others, so a single analysis for total beryllium, even though accurate, may be of limited value. The common gases sulfur dioxide and nitrogen dioxide both enjoy 5 parts per million threshold limit values. The proposed air quality standards are below one-tenth part per million, and yet the principal effect of both of these gases is irritation of the upper respiratory system and lungs. Nevertheless, the limits imply that a man can work safely in five parts per million of one of these irritant gases, while the gen-
eral public may suffer ill effects at one tenth part per million or less ! Similar observations could be made regarding carbon monoxide and a number of other substances, but I believe these illustrations serve to show the nature of problems which have arisen, and which will continue to arise as more air quality standards are set. The analytical chemist must play an active role in selecting numbers to be used as standards, and must understand the arguments brought to bear on them by many interested groups. It is my opinion that if widespread adoption of ambient air standards at levels currently under consideration comes to pass, and I suspect it will, then there will be serious questions raised concerning the validity of the threshold limit values. The result could be a stimulating period of reexamination of criteria, and a greatly intensified need for reliable, sensitive, and specific analytical methods.
The Analysis of Biological Tissues
One further concern of the analyst, related to the inhalation of contaminated air, is the so-called body burden of certain contaminants, most commonly metals, resulting from years of inhalation of substances which are not entirely
Figure 2. Particulate in lung (all species) 28 A
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ANALYTICAL CHEMISTRY
Circle No. 150 on Readers' Service Card-
REPORT FOR ANALYTICAL CHEMISTS
1H
Table 1. Suspended Particulate Matter"
Mean Maximum Daily Mg/m3 Loading, Mg/m 179 818 200 457 263 502 202 381 Wayne State University—U. S. Public Health Service air pollution study.
Year 1962 1963 1964 1965
two color reactions on one strip • :-•'.white center band acts as a contrast medium • hydrophobic center does not absorb moisture.
Duotest are indicator papers having a particularly high pH indicating accuracy and ease of visual evaluation. Each ribbon contains two complementary indicator-zones separated by a central white band, which enhances the contrast between the color zones and facilitates the appraisal of intermediate pH values. Being hydrophobic, the central white zone functions as a barrier when wet. Greater accuracy of measurement is assured, because the two indicators are prevented from running when wet. In addition, mechanical strength is improved as the center is moisture-proof.
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GIS
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30 A
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ANALYTICAL CHEMISTRY
excreted. The analytical chemist's role here is a very important one, for the term "trace metal analysis" is certainly descriptive of the need to determine minute quantities of these substances in the presence of large quantities of naturallyoccurring minerals. The analytical difficulties are great, so that considerable confusion may result from attempts to compare data. Compounding the confusion are the many ways in which tissue analysis data are reported, for example on the basis of the wet weight of the specimen, its dry weight, or its ash weight. Of greatest difficulty is the decision, on the basis of analytical data, to attribute the levels found to long-term inhalation of contaminated air. There is scarcely an element that cannot be found in most tissues, given a sufficiently large sample and a sensitive method, and it is well established that the diet alone can account for the presence of most of them. It is necessary, therefore, to establish that tissue levels are significantly elevated above some hypothetical normals to be sure that they could be due to inhalation exposure. It is extremely difficult to obtain tissue samples suitable for reaching firm conclusions, but a study performed
by our Department at Wayne State University for the U. S. Public Health Service afforded a unique opportunity to obtain meaningful data. A large group of animals lived several years in a room supplied with urban air containing typical quantities of contaminants, and an identical group lived in similar fashion, except that the air supply to the room was filtered, and contained virtually no particulate matter. Figure 2 shows a summary of data derived from histopathological examination of the lung tissues which attests to the success of the experiment. In general, the lungs of animals who lived in the clean air were clean-looking microscopically, while lungs from the unprotected animals contained substantially more imbedded particles. Even without microscopic confirmation, this difference was usually evident at autopsy, for the pleural surfaces were clear in the case of filtered-air animals, whereas dark spots were usually observed on the pleural surfaces of exposed animals. A summary of the total suspended particulate matter levels in the air which the animals breathed is shown in Table I. It can be seen that Detroit air at this location generally contained in excess of 200 /*g/m8, making it qualified to be
REPORT FOR ANALYTICAL CHEMISTS
First indicator paper with 0.1 to 14 pH range Table I I .
Mean Concentration of Gaseous Pollutants in Urban Air Study
Gas Units Exposure Chamber 1963 1964 1965 Mean for study Filtered Air Chamber
NEW FROM S'S
PANPEHA
1963 1964 1965 Mean for study
N0 2 NO S0 2 03 pphm pphm pphm pphm
CO ppm
C02 ppm
Hyrdocarbon* ppm
6.2 8.2 5.8 6.7
8.5 9.6 7.5 8.5
7.8 3.6 4.5 5.3
1.2 1.3 0.6 1.0
2.7 3.5 3.2 3.1
337 312 296 315
1.3 1.7 2.1 1.7
1.2 3.2 1.2 1.9
12.2 11.8 9.7 11.2
5.1 1.9 2.3 3.1
0.0 0.0 0.0 0.0
2.7 3.3 3.2 3.1
304 313 297 305
0.6 1.4 1.9 1.3
* p p m of CH 4
PAN-pH
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Availability S&S PAN-pH indicator papers are available in boxes containing 200 strips. Each box includes detailed instructions and a master color chart. Box is a sturdy fold-back type with a flip-top, for easy access to strips, which are approximately 3-3/8" long and 5 / 1 6 " wide.
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32 A
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ANALYTICAL CHEMISTRY
typical of urban air pollution in a large city. By contrast, the air in the filtered air room contained a negligible quantity of particulate matter, averaging
