Chapter 15 fourteen one in four

The biological struggle against cancer has a long history, the origins of which have long been obscured.But the original cause must have come from the natural environment.In the natural environment, no matter what kind of living things are inhabited, the earth is always affected by the sun, storms and ancient nature of the earth for good or bad.Some factors in this environment create disasters, and in the face of these disasters, life either adapts or is eliminated.Ultraviolet rays in the sun can cause malignant lesions.So can radiation from certain rocks, and arsenic leached from soil or rocks can contaminate food or water.

These hostile elements were present in the environment before the appearance of life; yet life appeared, and over the course of millions of years it has increased in number and variety.After the epoch of abundant time which belonged to nature, life reached a state of adaptation to the destructive forces; those less adapted were selectively eliminated, and only those most resistant species survived .These natural carcinogens are still a cause of malignancy, but they are now very few, and life has been accustomed from the first to their ancient mode of action. This changed with the advent of man, who, unlike all other forms of life, was able to create substances that produced cancer, known in medical terms as carcinogens.Some man-made carcinogens have been part of the environment for centuries.One example is fumes containing aromatics.With the advent of the Industrial Age, our world has become a place of ever-accelerating change.The natural environment is being rapidly replaced by an artificial environment composed of many new chemical and physical factors, many of which have a powerful ability to cause biological changes.People have not been able to protect themselves from these carcinogens created by their own activities. This is due to the slow evolution of human biological heredity, so it is also slow to adapt to new situations.As a result, these powerful carcinogens can easily overwhelm the body's weak defenses.

Cancer has been around for a long time, but our understanding of its causes has been slow and immature.Nearly two centuries ago, a physician in London first discovered that external or environmental factors could cause malignant lesions. In 1775, Mr. Postwall Porter declared that the common scrotal cancer among chimney sweeps must be related to the accumulation of soot in their bodies.He was not yet able to provide the "evidence" we demand today, but modern research methods have now isolated the lethal chemical from the soot and vindicated him. Porter discovered that certain chemicals in the human environment can cause cancer through repeated skin contact, inhalation or ingestion.In the more than a century after its discovery, there has not been much new progress in this understanding.Indeed, an epidemic of skin cancer has long been noted among workers exposed to arsenic vapors in copper smelters and tin foundries in Cornell and Wales.It was recognized that workers at the cobalt mines in Sikessoni and the uranium mines in Jochsel in Bohemia were suffering from a lung disease that was later diagnosed as cancer.These, however, were phenomena of the mines; but after the mass production of industry itself, these products invaded almost every living being in the environment.

During the last quarter of the nineteenth century, malignancies of industrial origin were recognized.About the time Pasteur was discovering that microbes were the cause of many infectious diseases, others were uncovering the chemical causes of cancer—skin and other cancers occurred among workers in the nascent Saxon lignite industry and the Scottish shale industry. due to occupational exposure to asphalt and asphalt.Near the end of the nineteenth century, six industrial carcinogens were known, and the twentieth century created countless new carcinogenic chemicals and brought the masses into close contact with them.Environmental conditions have changed widely in the less than two centuries since Porter's work.Exposure to hazardous chemicals is no longer limited to occupational exposure; these chemicals are in the environment of everyone's life—even children and the as yet unborn.It is not surprising, therefore, that we now see a dramatic increase in this malignancy.

This increase in malignancy itself is not just a subjective imagination. The July 1959 Census Office Monthly Bulletin reported an increase in lumbar venereal disease, which included malignant transformation of the lymphoid and hematopoietic tissues, with a mortality rate of 15% in 1958 compared to 4% in 1900.Judging by the current incidence of the disease, the American Cancer Society estimates that 45 million Americans alive today will eventually develop cancer.This means that two out of every three families will suffer from malignancy. What happens among children is even more deeply disturbing. Twenty-five years ago, cancer in children was considered a medical rarity.And today, more American schoolchildren die from cancer than from any other disease.The situation had become so serious that Boston opened the first hospital in the United States to treat childhood cancer.Cancer is responsible for 12% of all deaths among children aged 1-14.A large number of malignant tumors are clinically found in children under 5 years of age.However, what is even more frightening is that this kind of malignant tumor has increased rapidly in a large number of existing babies who have been born or are about to be born.Dr. W. C. Hueper of the American Cancer Institute, one of the earliest authorities on environmental cancers, pointed out that congenital cancers and cancers in infants may be related to the mother's exposure to carcinogens during pregnancy, which enter the placenta and act in rapidly developing fetal tissue.Experiments have shown that the younger the animal is exposed to carcinogenic factors, the more likely it is to get cancer.Dr. Francis Ray of the University of Florida warned: "We may be causing cancer in children today because of chemicals in our food... We can't imagine what will happen in a generation or two. as a result of."

A question that concerns us here is which of the chemicals we use in our attempts to control nature play a direct or indirect role in the development of cancer.Relying on conclusions drawn from animal experiments: we shall see five, possibly six pesticides that must definitely be rated as carcinogens.If we add those chemicals that some doctors believe can cause leukocytosis in humans, the list of carcinogens will be greatly lengthened.Here, the conclusion is speculative according to the circumstances, and since we cannot conduct experiments on human beings, the conclusion can only be like this; but this conclusion is still unforgettable.When we include those chemicals that are indirectly carcinogenic to living tissues or cells, then a few more pesticides are added to the list.

One of the earliest pesticides linked to cancer was arsenic, which appeared as a herbicide in the form of sodium arsenate.In humans and animals, cancer has been associated with arsenic for a long time.A curious example of the consequences of exposure to arsenic, according to Dr. Hueper in his book "Occupational Oncology," is a monograph on the subject.The city of Reichenstein in Silesia has been mined for gold and silver for almost a thousand years, and for hundreds of years for arsenic.For centuries, arsenic-containing wastes have piled up near the mines, and mountain water has washed away the arsenic contained in the waste.Groundwater was also contaminated, allowing arsenic to enter drinking water.Over the centuries, many of the local population contracted a disease that you later called "Reichenstein's disease," a chronic arsenic action that caused liver, skin, digestive, and nervous system disturbances.Malignant tumors often co-occur with this mental illness.Now, Reichenstein's disease has only historical significance.The arsenic has been largely removed from the water since it was switched to a new water source twenty-five years ago.Similarly, in Cordoba Province, Argentina, where drinking water from arsenic-bearing rock formations has become contaminated, an endemic chronic arsenicosis causing arsenic skin cancer has emerged.

It is not difficult to create a situation similar to that of Fuchenstein and Cordoba through the long-term use of arsenic-containing pesticides.Arsenic-soaked soils can easily contaminate water supplies in the tobacco-growing and many orchard regions of the northwestern United States, as well as in the cranberry-growing regions of the East. An arsenic-contaminated environment not only affects humans, but animals as well. In 1936, a very interesting report came from Germany.Near Freiberg in Saxony, silver and lead smelters spewed arsenic-containing gases into the air, which drifted into the surrounding countryside and landed on vegetation.Horses, cows, yams and piglets, which of course all feed on these plants, all exhibited hair loss and thickened skin, according to Dr. Hueper.Deer that inhabit nearby forests also sometimes develop abnormally pigmented spots and precancerous swellings.A swelling is the obvious lesion of a cancer.Both domestic and wild animals were affected by "arsenic enteritis, gastric ulcers, and cirrhosis of the liver."Sheep grazing near the smelter developed sinus cancer; when they died, arsenic was detected in its brain, liver and tumors.In the area, too, there was "a large number of insect die-offs, especially bees. After the rains, the rain washed the arsenic dust off the leaves and carried it into the creeks and ponds, and a large number of fish died. "

One carcinogen belonging to the group of newer organic pesticides is a chemical widely used against mites and ticks.The history of this pesticide amply demonstrates that while the law tried to protect the public, legal action to control the poisoning proceeded too slowly, resulting in years of exposure to a known carcinogen before a verdict. middle.From another point of view, this process is very interesting.It proves that what is required to be accepted by the public today may seem "very safe" today, but it may become extremely dangerous tomorrow. When the chemical was introduced in 1955, the manufacturer came up with a tolerance that would allow a small amount of residue to be present in the food crops it was treated with.As required by law, he has tested the chemical on laboratory animals and submitted his results.Scientists at the Food and Drug Administration, however, believed that these tests showed the chemical's possible carcinogenic potential, so the agency's commissioners proposed a "zero tolerance" for food shipped across state lines. No residues are legally allowed.However, the manufacturer has the right to appeal, so the case was re-examined by the Commission.The committee made a compromise decision: set a tolerance of 1 part per million and keep the product on the market for two years, during which time further experiments were conducted to determine whether the chemical was actually carcinogenic thing.

While the committee doesn't say so, its decision means the public will have to act as guinea pigs, testing suspected carcinogens alongside lab dogs and rats.However, animal experiments quickly came to a conclusion. Two years later, it was found out that this acaricide was indeed a carcinogen, and its residual poison was also polluting the food sold to the public.Even in this case, in 1957, the Food and Drug Administration could not immediately abolish the residue tolerance for this known carcinogen.In the following year, it took another year to carry out various legal procedures.Finally, in December 1958, the zero allowance proposed by the Food and Drug Administration Committee in 1955 became effective.

These are by no means the only carcinogens.In laboratory tests on animals, DDT produced suspicious liver tumors.Scientists at the Food and Drug Administration who reported the tumor findings are now uncertain about classifying the tumors, but feel that "it is reasonable to think of them as a low-grade hepatocellular carcinoma." Dr. Hueper now gives A clear evaluation of DDT - "chemical carcinogen". Two herbicides belonging to the carbamate group, IPC and CIPC, have been found to act to cause skin tumors in mice, some of which were malignant.Malignant lesions appear to have been induced by these chemicals, and it was possible that other kinds of chemicals prevailing in the outside world later contributed to the complete formation of the lesions. The herbicide aminotriazole has caused thyroid cancer in experimental animals. In 1959, the chemical was abused by many cranberry growers, and residues appeared in some of the berries on the market.The confiscation of tainted oranges by the Food and Drug Administration sparked controversy, complaints, and even many of the scientific facts presented by the FDA clearly demonstrated the carcinogenic properties of aminotriazoles in laboratory rats.When the animals were fed drinking water containing 100 parts per million of the substance (one spoonful of the chemical for every 10,000 spoonfuls of water), they started developing thyroid tumors at 68 weeks.After two years, the tumors, which were diagnosed as various benign and malignant tumors, appeared in more than half of the mice examined.These tumors also appeared at lower levels administered -- in fact, no low level had ever been found that did not cause tumors.Of course, no one knows at what level aminotriazoles would be carcinogenic in humans, but, as Dr. David Lutzton, a professor of medicine at Haward University, points out, there seems to be a standard level , this level may seem inconspicuous, but it has a lot to do with people. So far, there has not been sufficient time to understand the full impact of new chlorinated hydrocarbon insecticides and modern herbicides.Most malignancies develop slowly, taking a considerable part of the victim's life before clinical symptoms appear.In the early 1920s, women who painted luminescent material on the face of their clocks ingested small amounts of radium when their lips touched a brush; some of these women developed bone cancer fifteen or more years later.Some cancers arising from occupational exposure to chemical carcinogens manifest over a period of fifteen to thirty years or more. In contrast to these industrial exposures to various carcinogens, the dates of first human exposure to DDT were approximately 1942 (when DDT was used by military personnel) and 1945 (when used by civilians), and until the early 1950s, each Various chemical pesticides are used.These chemicals have sown the seeds of all kinds of malignancy, and the maturity of these seeds is coming. A long latency period is a general phenomenon for most malignancies; however, there is a now-known exception.The exception to this is leukocytosis.Leukocytosis began in Hiroshima survivors only three years after the atomic bombing, and there is currently no reason to think that a shorter incubation period would exist.Perhaps sooner or later other types of cancer will be found to have a relatively shorter latency period, but at the moment leukaemia appears to be an exception to the general rule that cancers develop very slowly. In this modern age of pesticides, the incidence of leukemia has been rising steadily.Figures from the National Office of Vital Statistics clearly show a sharp increase in blood malignancies. In 1960, there were 12,290 victims of leukemia alone.Deaths from all types of hematologic and lymphoid malignancies rose from 16,690 in 1950 to 25,400 in 1960.The death rate increased from 11.1/100,000 in 1950 to 14.1/100,000 in 1960.This increase is not only in the United States, but in all other countries, the number of registered leukemia deaths of all ages is increasing at a rate of 4-5% per year.What does this mean?Are people now increasingly being exposed to a toxin or agents that are foreign to our environment? Many world-renowned institutions such as the Mayo Clinic have diagnosed hundreds of victims of these diseases of the blood organs.Without exception, these patients had been exposed to a variety of toxic chemicals, including sprays containing DDT, chlordane, Agents of Benzene, Hexamethanol, and Petroleum Distillates. Dr. Hargraves believes that environmental diseases related to the use of various toxic substances have been on the rise, "especially in the last decade".From his extensive clinical experience he believes that "the vast majority of patients with hematological and lymphatic disorders have a compelling history of exposure to a variety of hydrocarbons including most of the pesticides seen today. A careful medical history The records will almost certainly show this relationship." The specialist now has a large number of patient-by-patient detailed medical records, and he notes among these cases leukemia, dysplastic anemia, Hawkins' disease, and other blood and hematopoietic Disorganization of organization."All of them had substantial exposure to these environmental carcinogens," he reported. What do these medical records show?One of them was the case of a housewife who hated spiders.In mid-August, she brought an aerial spray containing DDT and petroleum distillate into her basement.She sprayed the basement thoroughly.She had sprayed under the stairs, in the fruit cabinet, in all the protected places around the ceiling and rafters.When she finished spraying, she started to feel very sick, feeling sick, very irritable and nervous.During the next few days she felt better; however, it was evident that she had not thought of the cause of her illness; in September she repeated the whole process: she went for two more sprays, and when she sprayed, She fell ill and recovered temporarily.After she sprayed the air for the third time, new symptoms appeared: fever, joint pain and some malaise, and acute phlebitis in one leg.Upon examination by Dr. Hargraves, she was found to have acute leukemia.She died within the second month. Another of Dr. Hargraves' patients was a professional who worked in an old building infested with cockroaches.Since the insects bothered him, he took control measures himself.He spent the better part of a Sunday spraying the basement and all compartmentalized areas.The spray was 25% DDT in suspension in a solution containing methylnaphthalene.After a while he began to show subcutaneous bleeding and vomit blood.He was bleeding profusely when he entered the clinic.Studies of his blood revealed a severe weakening of the bone marrow known as dysplastic anemia.Over the next five and a half months, he received 59 blood transfusions, among other treatments, and he partially recovered, but some nine years later, he contracted the disease-causing leukemia. Where pesticides are mentioned in the medical records, the most prominent chemicals are DDT, HHC, hexachlorobenzene, nitrophenol, common beetle crystal para-dichlorobenzene, chlordane, and of course dissolved Drug solvents.As one physician emphasized, exposure to a single chemical is more of a special case than a rule; since these commercial products often contain a complex of There are also some impurities in the petroleum fractions used to make suspensions.Solvents containing aromatic and unsaturated hydrocarbons themselves may be the main factor causing damage to hematopoietic organs.From a practical point of view (rather than from a medical point of view), this difference is unimportant, since these petroleum spirits are after all an indispensable part of the most common spraying operations. There are many interesting cases documented in the medical literature in the United States and other countries that support Dr. Hargraves' belief in a causal relationship between these chemicals and leukemia and other blood disorders.These cases include a variety of everyday people: a farmer who was poisoned by his own spraying equipment or sprayed by an airplane, a college student who sprayed his study to kill ants and stayed there to study, a A woman who installed a portable HC66 sprayer in her home, a worker who worked in a cotton field sprayed with chlordane and toxaphene, etc.These medical records, half-cloaked in their technical medical jargon, hide many such human tragedies as two cousins ​​in Czechoslovakia, two children who lived in the same town and always worked and played together.One of their last, and deadliest, jobs was unloading bags of pesticides (hexachlorobiphenyls) at a farm complex.Eight months later, one of the children fell ill with leukemia and died nine days later.That's when his brother started feeling tired and running a fever.Within three months, his symptoms became more severe.Finally he too was hospitalized, again with acute leukemia and again with a fatal outcome. The case of another Swedish farmer is eerily reminiscent of that of the Japanese Ura Kuboyama on the tuna fishing vessel Fukuryu.Just like Kuboyama, the Swedish farmer has always been a healthy man, working as hard on the land as Kuboyama lives off the sea.The poison drifting down from the sky brought each of them a death sentence.The former is poisonous radioactive fallout, while the latter is chemical dust.The farmer treated approximately 60 acres of land with a powder containing DDT and HCB.As he worked, gusts of wind blew the smoke of the powder around him.That night, he felt unusually sleepy, and for the next few days he felt weak, with back pain, leg pain, and chills.He was forced to go to bed, and the Lutheran report said: "His condition deteriorated and on May 19 (one week after the spraying) he required hospitalization." He had a high fever and abnormal blood counts.He was transferred to Great Lutheran Infirmary, where he died after two and a half months of illness.An autopsy revealed that his bone marrow was completely atrophied. Such a very important normal movement process as cell division can be changed, this phenomenon is abnormal and destructive, and has become a big problem at present; it has attracted the attention of countless scientists, and it has cost an unknown amount of money .What exactly happened in a cell that turned regular cell growth into an uncontrollable proliferation of cancerous tumors? If answers are to be found in the future, they must be varied.Just as cancer itself presents various forms, its appearance forms are also different due to the difference in its etiology, development process and factors controlling its growth or outcome; therefore, cancer must have a corresponding variety of etiologies exist.Among them, those that damage cells may be only a few of the most basic types.All over the world, extensive research is sometimes conducted not at all as a cancer specialty.In the course of our research, we have seen a dim light that will one day illuminate this question. Once again, we have discovered that simply by looking at the smallest unit of life, the cell and its chromosomes, we can gain the additional information necessary to pierce the fog of mystery.Here, in this microcosm, we must look for factors that somehow alter the cell's wonderful mechanism of action and take it out of its normal state. One of the most memorable theories about the origin of cancer cells was put forward by a German biochemist, Professor Otto Warburg, who worked at the Max Planck Institute for Cell Physiology.Warburg devoted his entire life to the study of the complex process of oxidation in cells.As a result of his extensive basic research, he produced a compelling and lucid explanation of how normal cells become cancerous. Warburg believed that carcinogens, whether radioactive or chemical, deprived cells of energy by disrupting normal cellular respiration.This effect can be caused by frequent, repeated exposure to small doses.Once this effect is caused, it cannot be undone.Those cells not directly killed by the onslaught of the respiratory toxin will struggle to compensate for lost energy.They can no longer go on with that marvelous and efficient cycle of producing large amounts of ATP, so they revert to a primitive, terribly inefficient way of respiration by fermentation.The struggle for survival by means of fermentation often goes on for a long time.This fermentative respiration method is passed on through subsequent cell divisions, so that all subsequent cells have this abnormal respiration method.Once a cell has lost its normal respiration, it cannot regain it—not for a year, or a generation, or even many generations.But in this fierce struggle to regain lost energy, the surviving cells begin to compensate, bit by bit, with newly generated fermentation.This is the Darwinian struggle for existence, in which only the fittest and most adaptable organisms survive.Eventually, the cells reach a state in which fermentation produces as much energy as respiration.In this state, cancer cells can be said to have been created from normal body cells. Warburg's theory illuminates many other puzzling things.The long incubation period of most cancers is the time it takes for cells to divide indefinitely, during which time fermentation builds up as respiration begins to be disrupted.It takes a certain amount of time for fermentation to develop into a dominant position. Because the fermentation speed is different in different organisms, the time required in different organisms also varies: in mice, this time is relatively short, so cancer appears quickly in mice; This time is longer (even decades) on people, so the development of cancerous lesions on people is very slow. Warburg's theory also explains why, in some cases, repeated small doses of carcinogens are more dangerous than single large doses.A large dose of poisoning kills cells immediately, whereas a small dose allows some cells to survive, albeit in a threatened state.These surviving cells can later develop into cancer cells.This is why there is no single "safe" dose for carcinogens. In Warburg's theory we also find an explanation for another incomprehensible fact—the same factor can both cure and cause cancer.We all know this is the case with radiation, which can both kill cancer cells and cause cancer.The same is true of many of the chemicals currently being used to fight cancer.Why?Because both types of factors impair respiration.The respiration of cancer cells has already been damaged, so if some damage is added, it will die.The normal cell's respiration is compromised for the first time, so instead of being killed, it starts down a path that could eventually lead to cancer. Warburg's ideas were confirmed in 1953 when other researchers were able to turn normal cells into cancer cells simply by shutting them down intermittently for extended periods of time. In 1961, his ideas were proved again, this time not with artificially cultured tissues, but with experiments on live animals.Radioactive tracers were injected into cancerous mice, and the respiration of the mice was carefully measured. It was found that the rate of fermentation was significantly higher than normal, just as Warburg expected.Using the standards established by Warburg, most of the pesticides meet the standards of the most serious carcinogens.As we have seen in previous chapters, many chlorinated hydrocarbons, phenols, and some herbicides interfere with oxidation and energy production in cells.Thus, they can create dormant cancer cells in which an irreversible cancerous change will lie dormant for so long that it will go undetected until its cause has long been forgotten or is no longer recognized. When suspected, these cells emerge in broad daylight as an overt cancer. Another road to cancer may be caused by chromosomes.Many of the leading researchers in this field view with suspicion any factor that harms chromosomes, interferes with cell division, or causes mutations.In the eyes of these people, any mutation is a potential cause of cancer.While the mutation debate often involves mutations in embryonic cells whose effects may not be discovered until generations to come, mutations exist in cells of the body, too.According to the theory that cancer originates from mutation, a cell may mutate under the action of radiation or chemical drugs. This mutation makes the cell get rid of the body's control of maintaining normal cell division. Proliferated in irregular and irregular forms.Since the new cells are the product of this division, they have the same ability not to be controlled by the body, and over a long enough period these cells accumulate to form a cancerous tumor. Other researchers have pointed to the fact that chromosomes in cancerous tissue are unstable; they are prone to breaking or becoming damaged; the number of chromosomes is also abnormal, and there may even be two sets of chromosomes in a single cell. The first researchers to study the progression from chromosomal abnormality to true cancer were Albert Levan and J. J. Bessel at the Sloan-Kettering Cancer Institute in New York.When considering which of malignant lesions and chromosomal destruction came first, these investigators said without hesitation: "The abnormal change of chromosomes occurred before the malignant lesions." Perhaps, they speculated, there was a difference between the initial chromosomal destruction and the chromosomal destruction. After the chromosomal instability caused by this occurs, it takes a long time for disasters and errors to be implemented in many generations of cells (this is the long incubation period of malignant lesions), and this long period of time allows mutations to be concentrated and accumulated Get up, and let the cells get out of control and start irregular proliferation. This hyperplasia is cancer. Euclid Unci, one of the early proponents of the theory of chromosome stability, found the phenomenon of chromosome doubling particularly interesting.Based on repeated observations that hexachlorobenzene and its cognate homotrimer, hexahexa, are known to cause chromosome doubling in experimental plant cells, and that these chemicals have been implicated in many cases of fatal anemia with reliable diagnostic evidence, then the difference between the two Is there an internal connection between them?Which of the many pesticides interfere with cell division, damage chromosomes and cause mutations? It is easy to see why leukemia should be one of the most common diseases caused by exposure to radiation or chemicals that act similarly to radiation.The main targets of physical or chemical mutagen are those cells that are particularly active in dividing.This includes many tissues, but most importantly those involved in the manufacture of blood.Bone marrow is the main producer of red blood cells throughout life, and it releases nearly 10 million new red blood cells into the human blood every second.White blood cells are formed at a variable, but still enormous rate in the lymph glands and some bone marrow cells. Certain chemicals, which remind us again of the radioactive product strontium 90, have a special affinity for the bone marrow.Benzene, a common constituent of insecticide solvents, settles in the bone marrow where it can be deposited for as long as twenty months.Benzene itself has been identified in the medical literature as a cause of leukemia for many years. Rapidly growing childhood tissue also provides an optimal condition for the development of cancerous cells.Mr. McWarren Burnett pointed out that not only is leukemia increasing worldwide, but it has become extremely common in the 3-4 age group, an age when children do not show a high incidence of other diseases, According to this authority: "This peak of leukemia incidence between the ages of 3 and 4 years is difficult to find any explanation other than the exposure of these children to mutagenic stimuli before and after birth." Another mutagen known to cause cancer is urethane.When pregnant mice were treated with the chemical, not only did the mothers develop lung cancer, but so did the pups.In this experiment, the only possible exposure of pups to urethane was before birth, demonstrating that the chemical must have crossed the placenta.As Dr. Hueper has warned, in people exposed to urethane and its related chemicals, there is a possibility of developing tumors in infants due to prenatal exposure to the chemicals. Urethanes like carbamates are chemically related to the herbicides IPC and CIPC.不顾癌症专家们的警告，氨基甲酸酯已被广泛使用，不仅用作杀虫剂、除草剂、灭菌剂，而且还用在增塑剂、医药、衣料和绝缘材料等各种产品中。 通向癌症的道路也可能是间接的。有些物质一般来说不是致癌物，但它可以妨碍身体某些部分的正常功能，并由此引起恶性病变。有一些癌症可作为重要的例子，特别是生殖系统的癌症，它们的出现与性激素平衡被破坏有一定联系；在某些情况下，这些性激素的破坏反过来又引起一些后果，这些后果影响了肝脏保持这些激素正常水平的能力。氯化烃正好是这种类型的因素，因为所有氯化烃对肝脏在一定程度上都是有毒的，所以它能够招致这种间接的致癌作用。 当然，性激素在体内是可以正常存在的，并且起着一种与各种生殖器官有关的、必不可少的、刺激生长的作用。然而，身体具有一种长期建立起来的保护作用来消除激素的多余积累，肝脏起着一种保持雄、雌性激素之间平衡的作用(不管是哪种性别都产生雄性激素和雌性激素，虽然数量比例不同)，肝脏可以阻止任何一种激素的过多积累。然而，如果肝脏受到疾病或化学物质危害，或如果维生素B供应不足，肝脏的上述功能就会被破坏。在这种状况下，雌性激素就会达到一个异常高的水平。 后果如何呢？至少在动物方面有大量的实验证据。其中一例如下，洛克菲勒医学研究所的一个研究人员发现，由于疾病而使肝脏受损的兔子表现出子宫肿瘤的高发病率，研究人员认为子宫肿瘤高发的形成是因为肝脏已不能再抑制血液中的雌性激素，以致于“最后这些肿瘤演化到癌变的水平”。对小白属、大白鼠、豚鼠和猴子的广泛实验表明，长期服入雌性激素只需小剂量已能引起生殖器官组织的变化，“从良性蔓延变化到明显的恶性病变”。通过服入雌性激素，欧洲大鼠也诱发出肾脏肿瘤。 虽然在这个问题上存在着不同的医学观点，但大量证据支持这样一种观点，即同样的影响也会发生在人的组织中。穆斯格尔大学维多利亚皇家医院的研究人员发现他们所研究过的150例子宫癌中有三分之二提供了证据，证明体内雌性激素含量水平异常的高。后来又有20个病例，其中90%都具有高活动性的雌性激素。 虽然用所有现代医学的实验手段也检查不出肝脏有什么损害，但这个人仍可能已得了足以干扰消除雌性激素的肝损害。氯化烃很容易引起这种情况，如我们所知，氯化烃摄入量很低就引起了肝细胞的变化，它们也同样引起维生素B的损失。这一情况极为重要，因为其他环节的证据表明这种维生素具有抵制癌症的保护作用。 以后的C·P·洛兹(他一度担任斯朗-凯特林癌症研究所的指导者)发现，暴露于一种非常强烈的化学致癌物的实验动物，如果喂给他们酵母——一种天然维生素B的丰富来源，它们就不会出现癌症。这种维生素的缺乏也被发现与口腔癌，可能还有消化道其他部分的癌相伴随。这一情况不仅在美国观察到了，而且在瑞典和芬兰遥远的北部地区也发现了，这些地方的日常食物通常缺少维生素。容易得早期肝癌的人群，例如非洲斑图部落，他们典型地遭受着营养缺乏。男性胸癌在非洲一些地方也占优势，此情况与肝病相营养不良有关。在战后，希腊的男性胸癌的增多是饥饿时期的一个普通伴随物。 简言之，关于农药在癌症中的间接作用的讨论是由于已证实它们具有损害肝脏和减少维生素B供给的能力，这就导致了体内自生的雌性激素的增多，也就是说由身体本身产生了这些物质。现在还有大量各种的人工合成雌性激素正在加入到我们环境中来，我们正日益严重地暴露在这些物质之中——它们存在于化妆品中、医药中、食物中和职业性暴露中。这种联合的影响是一件值得极为关注的事情。 人类暴露于致癌化学物质(包括农药)中是难以控制的，并且也是多种多样的。一个人可以通过许多不同的暴露途径摄入同一种化学物质。砷就是一个例子。它存在于许多具有不同形式的环境之中：作为空气污染物存在，作为水的污染物存在，作为食物残毒存在，作为医药存在，作为化妆品存在，作为木料防腐剂存在，或是作为油漆和墨水中的染料存在等。十分可能的是，这些暴露方式中没有哪一种能单独使人类陷入恶性病变。——但是任何单独的一种假定的“安全剂量”都可能压翻已经负载了许多其他种“安全剂量”的天平。 另外，人类的恶性病变也可以由二、三种不同致癌物的共同作用所造成，因而存在着一个它们作用的综合影响。例如，一个暴露于DDT的人几乎同时也暴露于烃类之中，而这些烃类是作为溶剂、颜料展开剂、减速剂、干洗涤剂和麻醉剂而被广泛使用着。DDT的“安全剂量”在这种情况下又有什么意义呢？ 上述情况由于这样一个事实而变得更加复杂化，即一种化学物质可以作用于另一种化学物质而改变其作用效果。癌症有时需要两种化学物质互相影响才能发生，其中一种化学物质先使细胞或组织变得敏惑，然后在另一种化学物质或促进因素的作用下细胞或组织才发生真正的癌变。这样，除草剂IPC和CIPC就在皮肤癌的发生中起了带头者的作用，它播下了癌变的种子，而当另外一些东西(也许是普通的洗涤剂)进入人体作用时，癌变就会在人体中发生。 更进一步说，在物理因素与化学因素之间也可能存在着相互作用。白血病的发生过程可能分为两个阶段，恶性病变的开始是由X射线引起的，而摄入的化学物质(如尿脘)则起了促进的作用。人群在各种来源的放射性中暴露的日益增加，再加上各种化学物质与人体的大量接触，这一切给现代世界提出了一个严峻的新问题。 放射性物质对供水的污染提出了另外一个问题。由于水中常包含着许多化学物质，那些成为水的污染物的放射性物质可以通过游离射线的撞击作用而活跃地改变水中这些化学物质的性质，使这些物质的原子以不可预测的方式重新排列组合而创造出新的化学物质来。 洗涤剂是一个特别普遍的污染物，现在成了一个公共供水中的麻烦问题，全美国的水污染专家们都在关心着它，但还没有实际可行的办法来处理掉它。现在人们几乎还不知道有什么洗涤剂是致癌物，但洗涤剂可能通过一种间接的方式促进癌变，它们作用于消化道内壁，使机体组织发生变化，以使这些组织更容易吸收危险的化学物质，从而加重了化学物质的影响。不过，谁能预见和控制这种作用呢？在这错综变幻的万花筒中，致癌物，除了“零剂量”还有什么剂量是“安全”的呢？ 我们容忍致癌因素在环境中存在，我们就要对它可能产生的危险负责。这一危险已经被当前发生的情况清楚地描绘出来了。1961年春天在许多联邦的、州的和私人的鱼类产卵地，在虹鳟鱼中出现了一种肝癌流行病。在美国西部和东部地区的鳟鱼都受到了影响；超过三龄的鳟鱼实际上百分之百地得了癌症。之所以能得知这一发现，是由于全国癌症研究所环境癌症科和鱼类与野生物服务处已事先在报告所有鱼类的肿瘤方面达成了一个协定，这样做的目的是为了能够由水质污染发出对人类癌症危险的早期警告。 尽管研究工作至今还在寻找在如此广阔地区发生这种流行病的确切原因，但最好的证据莫过于指出在事先准备好的鱼类产卵地的饵料中已存在着问题。这些饵料含有令人难以置信的各种化学添加物和医药，它们都混入了基本食料之中。 这个鳟鱼的事件从许多方面来看都有重要意义，但是最重要的一点是，它作为一个例子说明了当一个强烈的致癌物被引入环境时，将会发生什么事情。惠帕博士把这一流行病看作是一个前车之鉴，它警告人们必须把极大的注意力放在对数量巨大、种类繁多的环境致癌物的控制上面。他说：“如果不采取这样的预防措施，那么在鳟鱼身上表现出来的这场灾难必将会与日俱增地在人类的未来出现。” 由于发现我们正生活在一个如一位研究者所你的“致癌物的汪洋大海之中”，这当然令人沮丧，并很容易使人产生绝望和失败的反应。一个普遍的反应是：“这难道不是一个毫无希望的情况吗？”“难道没有可能从我们世界上去尝试消除这些致癌因素吗？最好不要再浪费时间去进行试验了，干脆把我们全部力量用于去发现治疗癌症的良药，这样不更好吗？” 这一问题被提给了惠帕博士，他在癌症研究方面的多年卓越工作使得他的意见受人尊敬，他对这一问题深思熟虑了很长时间，他基于他一生的研究和经验进行判断，并作出了一个全面的回答。惠帕博士认为，我们今天因癌症而造成的形势与十九世纪最后几年人类面临传染病时的形势非常相似。病原生物与许多疾病间的病因关系已被巴斯德和卡介的辉煌研究工作所确立。医学界人士、甚至一般公众在当时都逐渐醒悟到人类环境已被大量的、能够引起疾病的微生物所占据，正如今天致癌物蔓延到我们周围一样。大多数的传染疾病现在已被置于适当的控制之下了，而且有些实际上已被消灭了。这一辉煌的医学成就是靠两面夹攻而实现的，——既强调了预防，又强调了治疗。且不管“神奇药丸”和“起死灵药”在外行人头脑中占有多么突出的地位，实际情况是，在抵抗传染病的战争中，真正具有决定性意义的大部分战役是由消灭环境中病原生物的措施组成的。一百多年前的伦敦霍乱大爆发是一个历史例证。一位名叫约翰·斯诺的伦敦医生把发病情况绘成了地图，他发现所有病例都发源于一个地区，这个地区的所有居民都从波罗德街上的同一个泵井里取水用。作为一个迅速、果断的预防医学行动，斯诺博士更换了那个泵井的把柄。该流行病由此就被控制住了——不是通过用一种药丸去杀死(当时尚未人知的)引起霍乱的微生物，而是把它们排除于人类环境之外。甚至从治疗手段来看也是这样，减少传染病的病灶比治疗病人更能取得成效。现在结核病已相对比较烯少的原因主要是与这样一个事实有关，即一般人现在很少有机会去和结核病病菌相接触。 今天我们发现我们的世界充满了致癌因素。将我们全部力量或大部分力量集中到治疗办法(甚至想能找到一种治愈癌的“良药”的这种攻克癌症的战斗，根据惠帕博士的见解将是要失败的，因为这种作法没有考虑到环境是致癌因素的最大的储存地，环境中的这些致癌因素继续危害新的牺牲者的速度将会超过至今还无从捉摸的“良药”能够制止癌症的速度。 以预防为主来与癌症斗争是一种常识性的办法，但为什么我们在采取这种办法的时候却总是这样迟缓呢？可能“是因为治疗癌症病人的目标此起预防癌症来更加激动人心，更加实在，更加引人注目和更加值得报酬吧，”惠帕博士这样说。然而，在癌症形成之前去预防癌症“确实是更为人道”，而且可能“比治疗癌症要有效得多”。惠帕博士几乎无法忍受这样一种满怀希望的想法，这种想法要求得到一种我们能在每天早上早饭前服用的神奇药丸，以保护我们免于癌症。公众之所以相信癌症能够这样被治住，其部分原因是出于一种误会，即误认为虽然癌症是一种神秘的疾病，它是一种由单一原因引起的单一疾病，因而也满怀希望能有一种单一的治疗办法治好它。当然，这和人们已知的真理相去很远。环境癌症就正好是由十分复杂的多种化学因素和物理因素所引起的，所以恶性病变本身就表现为多种不同的、在生物学上独立的形式。 这样一种期望已久的“突破”，假使有一天实现了，也不可能指望它是一种能治疗所有类型恶性病变的万灵药。虽然这种对“良药”的寻找还会作为一种治疗手段继续下去，以挽救和治疗那些已经得上癌症的受难者；但是宣扬只要有个锦囊妙计，问题就将会立刻解决的希望是对人类的一个损害。这个问题的解决将会一步一步慢慢到来。正当我们将几百万元倾倒到研究工作中时，正当我们把我们的全部希望寄于发现医治已患癌症病人方法的大规模计划的时候，甚至当我们寻求治疗措施的时候，我们却可能忽视了进行预防的可贵机会。 征服癌症的工作决不是毫无希望的。从一个重要的方面来看，现在的前景比十九世纪末控制传染病时的情况更加鼓舞人心。当时世界上充满了致病细菌，正像今天世界上充满了致癌物一样。不过，当时的人们并不曾把病菌散布到环境中去，人们当时只是无意识地传播了这些病菌。与之相反，现代人们自己把绝大部分致癌物散布到环境中去，如果他们希望的话，他们就能够消除许多致癌物。在我们世界上，致癌的化学因素已经通过两种途径建立了自己的掩体防线：第一，具有讽刺意味的是，由于人们追求更好的、更轻松的生活方式；第二，因为制造和贩卖这样的化学物质已经变成我们的经济和生活方式中一个可接受的部分。 要想让所有化学致癌物现在或将来能够全部从现代世界上消灭掉，这可能是不现实的。但是，相当大比例的化学致癌物决不是生活的必需品。随着这些致癌物的被消除，它们加给生命的总负荷量将会大大减轻，同时，每四个人中将有一个人发生癌症的威胁至少也会显著缓和下来。最顽强的努力应当用到消除这些致癌物上面去。它们现在正污染着我们的食物、我们的供水和我们的大气，并且这些致癌物是以最危险的接触方式——微量的、一年又一年反复进行暴露的方式出现的。 在进行癌症研究的最优秀的人们中间，有许多人与惠帕博士有共同的信念，他们都相信通过顽强地努力去查明环境致癌因素，并顽强地去消除或减少它们的冲击影响，恶性病变是可以有效被征服的。为了医治那些已患潜在癌症或明显癌症的人们，寻找治疗方法的努力当然必须继续进行下去。但是，对于那些尚未患癌症的人们，当然还有对那些尚未出生的后代，进行预防已是迫在眉睫的事。