subtle effects should be ascribed to lead exposure and/or to other factors.

Evidence was also presented at the symposium which suggests another important respect in which the effects of lead may be largely overlooked because of limitations in our existing knowledge. This aspect of the problem stems from the fact that some of the lead taken into the human body is stored in the bones.

Any of a number of factors-including such physiological stresses as peptic ulcer involving excessive bleeding and such physical trauma as accidents in the home or on the highways-may release lead previously held in storage. In such cases, the released lead may cause greater injury than the event which precipitated its release. Here again, the connection may never be made in the course of routine diagnosis and

treatment.

Existing evidence suggests that certain groups in the population may be particularly susceptible to lead injury. Children and pregnant women constitute two of the most important of such groups. Some studies have suggested an association between lead exposure and the occurrence of mental retardation among children.

Persons with anemia and certain kidney and liver diseases may also be especially vulnerable to the effects of lead. The limited information now available suggests that persons in all these groups may have a reduced capacity to dispose of the lead that enters the human body from the environment.

Mr. Chairman, I have attempted to provide a brief summary of the limited scientific knowledge now available on the effects of small amounts of lead in the human body. Clearly, this knowledge raises many questions that cannot be answered now but must be answered in the months and years ahead if we are to deal intelligently with the problem of environmental lead contamination.

We need to know a great deal more than we do now about the relative importance of the various ways in which lead enters the body. It is well established that lead is absorbed to a greater degree from the respiratory tract than from the digestive tract. It appears that most of the lead which people now take into their bodies comes from food. But there are indications that the pattern of human exposure to lead may be changing.

In this country, the total production and consumption of lead has remained more or less constant over the past two decades, but an important shift has taken place in the uses of it. As the chart indicates, there have been sharp increases in the use of lead additives in gasoline and in the use of lead in storage batteries. These increases are, of course, a reflection of the upward trend in the use of motor vehicles.

The upper line is the production of lead. The bottom line shows the shift from the use of lead in metal products and paints which has gone down over time whereas the use of storage batteries and gasoline additives has gone up.

This chart suggests that an increasing portion of total human exposure to lead may result from lead contamination of the atmosphere. As the consumption of leaded gasoline increases, discharges of lead into the air also increase. It has been estimated that 70 to 80 percent of the lead in gasoline is eventually emitted into the air, and there are data showing that much of it consists of particles of sizes that will remain suspended in the atmosphere for long periods of time.

The use of lead in storage batteries, which is also increasing, is not in itself a source of environmental lead contamination, but open burning and incineration of such batteries is a common practice which may make another substantial contribution to lead contamination of the

air.

One of the questions that must be answered is whether the total lead exposure of the general population is increasing. Environmental lead levels were never adequately measured prior to such developments as the initial use of lead compounds as additives to gasoline. A few

months ago, however, data were published which suggested that lead levels in the environment are rising. Further studies in this area are clearly needed.

In summary, Mr. Chairman, we in the Public Health Service are greatly concerned about the problem of environmental contamination. We now have under consideration a number of specific proposals for investigations which we hope will expand and improve our present inadequate knowledge of this modern environmental problem. Dr. Prindle will describe these proposals.

I am not suggesting that we undertake endless studies of scores of environmental contaminants. In Public Health, we cannot afford to wait for the last shred of evidence before instituting appropriate control action. That we need a much better understanding of many of our environmental contamination problems is clear, however. Until we reach such an understanding, Government and industry must clearly work together to minimize any hazard which may exist; wherever possible, the use of toxic materials that may reach the community envionment should be avoided or minimized.

And where the use of such materials is necessary, rigorous control measures should be instituted. It is essential that the American people have a margin of safety against the adverse effects of those environmental contaminants from which there is no effective refuge.. Thank you, Mr. Chairman.

I will be happy to answer any questions.

(The paper referred to earlier by Dr. Stewart is as follows:)

FURTHER DISCUSSION OF SELECTED ENVIRONMENTAL CONTAMINANTS

1. ARSENIC

The possible cancer-causing effects of arsenic have been studied more or less continuously for many years but without producing enough definitive information to settle the scientific controversy that surrounds the subject. The concern that exists is based on data suggesting that exposure to arsenic compounds may be associated with excessive lung cancer among workers in copper smelters and among people living in or near places where such smelters are located. The use of arsenic in pesticides is also suspected of being associated with an excessive incidence of lung cancer in agricultural workers, mainly among workers in European vineyards. The use of pesticides containing arsenic, which is declining, and smelting of copper and other metals, many of which contain arsenic, are among the principal routes by which this substance and its compounds reach the environment.

2. ASBESTOS

The occupational hazards of prolonged exposure to asbestos dust are widely known. The possible community environment hazards are a subject of increasing concern among scientists. In occupational situations, long-continued inhalation of asbestos dust is associated with an excessive incidence of certain types of cancer of the lung and pleural cavity. There is some evidence of a similar effect among persons living near asbestos mills. Occupational exposure to asbestos dust has also been linked with the occurrence of a chronic pulmonary disease similar to silicosis. The question of whether asbestos dust in the community environment may produce similar effects merits close investigation. In all likelihood, appreciable amounts of it reach the environment. Because of its durability and heat-resistance, asbestos is widely used in such products as brake linings, roofing, insulation, and household tile. Some of its uses involve almost constant wear, with the result that asbestos particles are released into the atmosphere.

3. BERYLLIUM

The use of beryllium has increased substantially in recent years. Because it adds many desirable properties to alloys, it has come into wide use in industry.

Also of growing concern is its use as a fuel for rocket engines. Beryllium and its compounds are highly toxic. Over the past 40 years, many cases of acute and chronic beryllium disease have been reported. Over 700 cases are now listed in the beryllium disease registry at the Massachusetts Institute of Technology. The great majority resulted from occupational exposures, but a disturbing number involved non-industrial persons, especially pregnant women, living near plants emitting small amounts of beryllium into the atmosphere. The respiratory organs, particularly the lungs, are the prime target of beryllium toxicity. The latent period between initial exposure to the material and the appearance of disease varies from a few months to 20 or more years. There is some evidence that beryllium compounds are capable of producing malignant tumors in monkeys.

4. CADMIUM

This highly toxic metal was once used to plate kitchen implements; its use for this purpose was stopped when cases of cadmium poisoning began to occur. But it still reaches the environment. There are, for example, measurable amounts of cadmium in suspended particulates in the air of urban communities. Though the amounts of cadmium to which most urban dwellers are ordinarily exposed are below the level capable of producing acute toxicity, they may be sufficient to produce serious impairment of health over long periods of exposure.

5. FLUORIDES

Fluorine compounds may reach the environment in either gaseous or particulate form. The dangers of fluoride pollution to human health are generally associated with relatively high environmental concentrations, compared to the minute amounts involved in fluoridation of drinking water. Among workers exposed to fluorides and, to some degree, among people living near industrial sources of fluorides, adverse effects attributable to these compounds have included irritation of the skin and mucous membranes, eye irritation, nosebleeds, inflammation of the respiratory tract, and diffculties in breathing. Also of great importance are the damaging effects of fluorides on livestock and vegetation; in some parts of the country, losses have been substantial. The manufacture of phosphate fertilizers is perhaps the best known source of fluoride pollution, but it is not the only one. Others include manufacture of aluminum and steel and the use of fluorine in rocket fuel. The present and potential future extent of fluoride pollution of the environment and its implications for public health have not been adequately evaluated.

6. MERCURY

The acute and chronic toxic effects of mercury are well known; the major effects are neurological. The extent to which mercury reaches the community environment is uncetrain, but its wide usage in scientific instruments and in metallurgical, chemical, paint, photoengraving, and pharmaceutical industries suggests that many opportunities exist for release of mercury compounds into the environment. Of equal, perhaps even greater, importance may be the hazards associated with heedless use of mercury in science classrooms and careless handling of instruments containing mercury. Such practices may result in liberation of mercury vapor into the air; its inhalation could be hazardous. The need for proper ventilation in rooms where mercury is being handled and for prompt clean-up of spilled mercury needs to be widely recognized.

7. PLASTICS

The principal reason for concern about plastics is that their disposal by burning may create highly toxic by-products. The combustion of certain types of plastics including teflon, fluorinated plastics, and vinyl plastics-gives rise to substances whose physiological effects may be similar to those of phosgene gas, a severe respiratory irritant used as a war gas in World War I. The practice of buring or incinerating plastics along with other refuse may pose no immediate problem, but it could become a widespread and very serious health hazard as. increasing amounts of plastics are used-and discarded. The problem of disposing of plastics is compounded by the fact that they do not decompose readily; moveover, with existing technology, there are no efficient or economical means of reclaiming plastics from such widely used items as food containers and other household goods.

Senator MUSKIE. Thank you very much, Dr. Stewart, for an excellent presentation. I think you have raised the red flags in such a clear fashion that I do not know that we can clarify the problem further with questions but I do have some that I would like to ask.

In your statement you say this: "We must understand, of course, that we do not need to choose between technological development on the one hand and the healthful environment on the other."

I take it what you mean by that and the remainder of your presentation, we could describe by borrowing from the terminology of nuclear science, what we need is a clean technology to achieve this?

Dr. STEWART. That is right.

Senator MUSKIE. Get away from the fogs which create hazards to health.

Dr. STEWART. That is right.

Senator MUSKIE. I would like to turn immediately to the question of the lead problem in order to establish continuity between your prepared testimony and this discussion. Now the easiest way to eliminate the lead problem would be to eliminate the use of lead in gasoline and elsewhere. Is that a recommendation that you would be prepared to make at this time?

Dr. STEWART. No, sir, we would not be ready to make that recommendation at this time.

Senator MUSKIE. In other words, you do not feel that the evidence as to the hazards of lead is sufficiently definite and clear at this point that such a recommendation is strongly indicated?

Dr. STEWART. Not at this time. Your question was the total elimination of lead from gasoline?

Senator MUSKIE. Yes.

Dr. STEWART. I do not think that we have evidence which would justify that procedure at this time.

Senator MUSKIE. In your statement there is this language: "It has been estimated that 70 to 80 percent of the lead in gasoline is eventually emitted into the air." Now on what is that estimate based?

Dr. STEWART. I am sorry, I was distracted, Mr. Chairman. I did not get the question.

Senator MUSKIE. Your statement says, "It has been estimated that 70 to 80 percent of the lead in gasoline is eventually emitted into the air." Upon what is that estimate based?

Dr. STEWART. On the studies that have been done on gasoline use, showing what comes out.

Senator MUSKIE. These are studies which you people have conducted?

Dr. STEWART. That is right.

Senator MUSKIE. There has been some concern for a long time as to whether or not there is a tendency for pollutants in the air to accumulate and to build up residues. You touch on this point on page 10 with respect to lead when you say there are data showing that much of this consists of particles and sizes that will remain suspended in the atmosphere for long periods of time. There is the possibility then that we are building up residues of lead in the air such that we will be forced to reduce the quantity of lead entering the atmosphere.

Dr. STEWART. Yes, I think this is correct, that there is some evidence to show that the amount of lead in the atmosphere is accumulating. I