From Industrial Toxins to Worldwide Pollutants: A Brief History of Polychlorinated Biphenyls

In 1944, Public Health Reports published the results of studies of acute toxicity in guinea pigs, rabbits, and rats exposed to chlorinated diphenyls, now better known as polychlorinated biphenyls, or PCBs (Box). In the studies, conducted by the Industrial Hygiene Research Laboratory of the National Institutes of Health, then-US Public Health Service surgeon J. W. Miller concluded the following: “Two conspicuous pathologic findings were observed—liver damage in all series of experiments and skin changes in the animals receiving subcutaneous injections or applications of the material to the skin.” Similarly, liver damage was reported “in animals who were fed PCBs during periods of 30 to 90 days.” ¹ This research built on previous studies of chlorinated diphenyls, most notably by Cecil Drinker and colleagues in the Journal of Industrial Hygiene and Toxicology, who also found systemic effects in animals from acute exposures to PCBs. ^{2 -4} Other studies in the 1930s documented the harmful effects of PCBs on workers in a factory that manufactured PCBs. ^{5 -7}

Box. The trade name of the polychlorinated biphenyl (PCB) studied was Aroclor 1242. PCBs are not a single chemical but a class of chemicals with a diphenyl core to which are attached anywhere from 1 to 10 chlorine atoms. Traditionally, the last 2 numbers in a PCB type denote the percentage by weight of chlorine in the PCB product; for example, Aroclor 1242 is 42% chlorine by weight.

This article seeks to explore the history of knowledge about the toxicity of PCBs to elucidate the relationship between occupational and environmental health and how the very same toxins that were defined as dangerous to workers in a factory later emerged as concerns to the broader public. Today, PCBs, chemicals that were virtually unknown in the late 1920s and that became mass produced only in the early 1930s, have become worldwide pollutants and judged probable human carcinogens. Indeed, the Centers for Disease Control and Prevention has documented that virtually everyone living in the United States has PCBs in their bodies. ⁸

In this installment of Public Health Chronicles, I examine PCBs as paradigmatic environmental pollutants that, like a host of synthetic materials created in the interwar decades and marketed broadly in the post–World War II era, are a major public health concern today. In part because of Rachel Carson’s groundbreaking work, Silent Spring, published in 1962, historians’ attention has focused on dichlorodiphenyltrichloroethane (DDT) and a few other pesticides such as dieldrin, aldrin, and endrin—other chlorinated hydrocarbons that were identified in the 1950s as environmental contaminants. But by 1950, the studies of DDT and related insecticides led the public health community to worry about the broader category of chlorinated hydrocarbons. That year, the American Public Health Association’s Committee on Chemicals Introduced in Foods issued a report that warned about the potential dangers of the widespread use of chlorinated hydrocarbons: “The chlorinated hydrocarbons…are soluble in fats and are stored in the fatty tissues of the body. These compounds possess a high order of toxicity, and their uncontrolled or unwise use is not desirable.” ⁹

In 1951, the House Select Committee to Investigate the Use of Chemicals in Food Products held hearings at which 62 chemicals were named as being used or proposed for use in food. Dr James O. Clarke, director of the Division of Program Research at the US Food and Drug Administration, explained why DDT was included in its study. He pointed out that “substances were chosen which were believed to be the most nearly representative of the chemicals in that particular use classification.” DDT was included “as a representative of a number of organic chlorides used as insecticides.” ¹⁰ The problems with DDT, a product produced in the laboratory, were quickly understood as more than just a threat to those who manufactured it.

One of the researchers who addressed the problems with DDT was Dr Morton Biskind, a physician who authored numerous articles on chlorinated hydrocarbons, including one on DDT poisoning. ¹¹ During the 1930s, he had been a staff member at the headquarters of the Council on Pharmacy and Chemistry of the American Medical Association and in the 1940s was in charge of the endocrine laboratory and endocrine clinic at Beth Israel Hospital in New York City, where he was then associate endocrinologist. He was also on the staff of the New York Hotel Trades Council Health Center. For the previous 2½ years, in the late 1940s, he was conducting clinical work in the Laboratory of Industrial Hygiene of New York State. Although DDT was the best known of the hydrocarbons, Biskind argued that

Without exception, every one of the chlorinated cyclic hydrocarbon insecticides is a liver poison. This is true of the entire series from the solvent monochlorobenzene and the mothicide paradichlorobenzene to DDT and the chlorinated napthalenes aldrin and dieldrin.…Exposure to this whole group of compounds is now universal in the United States, and it appears that few persons escape storage of these toxic agents in the body fat. ¹²

He saw the long-term effects of this group of insecticides as being particularly troubling because of the potential ecological and agricultural devastation that they could cause.

The extremely stable nature of the DDT group of insecticides poses another problem. In amounts normally used for growing of crops, severe poisoning of the soil has persisted for the entire duration of reported observations (7 years) and as no means are available to destroy these compounds, millions of acres of farmland may ultimately have to be withdrawn from cultivation since these substances not only inhibit the growth of many plants but also may be absorbed into the food portions in dangerous concentrations. ¹²

DDT and other pesticides garnered the most public attention during the 1950s because of their widespread distribution through the food chain. But the growing uses of electricity and the development of new chemicals, specifically PCBs, led to other concerns. Initially, PCBs were envisioned for a wide range of uses. Their major use was as a dielectric fluid to prevent sparking in transformers and capacitors. But from the very first, PCBs were envisioned for fireproofing, paints, varnishes, adhesives, lacquers, transparent and moisture-proof paper, heat-transfer fluid, impregnation, a wide range of plasticizers, inks, and even chewing gum (Swann Chemical Company unpublished document, “Use Codes,” January 1, 1935, Monsanto Archives). It was sold to be used “as protective and decorative coatings for wood, metal, brick, stone, concrete, and fabric surfaces” including “wood and metal used in the construction of yachts, barges, and other marine craft; structural steel for bridges, buildings, roofs, and power-line structures; masonry floors; walls; concrete swimming pools; and traffic paints” (pamphlet, “Monsanto Technical Bulletin No, P-124,” January 1, 1948, Monsanto Archives). In the 1940s and 1950s, in addition to being marketed as a soil poison and an insecticide extender, it was promoted for use in carbonless carbon paper, in hydraulic fluids, as an ingredient in dentures, and in other items. PCBs were designed to be chemically stable and fire resistant—qualities that made them useful in electrical equipment but also created a huge environmental risk. Virtually all of these early uses involved the likelihood that PCBs would end up in the environment, exposing humans, animals, and the ecological landscape to hundreds of millions of pounds of PCBs. Because of their chemical stability, they remained in the environment for long periods. As Monsanto, the sole producer of PCBs in the United States, stated in the mid-1930s, “Aroclors are used because of their qualities of moisture and gas proofness—their resistance to acids, alkalies, and ultra violet light—their electrical insulation and durability” (Pamphlet, “Monsanto Chemicals of the Swann Products Division,” Ca. 1935, Monsanto Archives).

By 1950, in addition to the potential dangers documented in the 1930s for those who were working in factories that manufactured PCBs, and the toxicological tests conducted in the 1930s and 1940s that had confirmed these potential dangers, further reports showed that workers who were exposed to PCBs in factories or settings that used them were at risk. In Brazil, Indiana, a plant that used PCBs in a heat-exchange system had a leak that caused a toxic reaction in 2 workers (Memo, “Aroclor” by R.E.K. [Dr Kelly], February 6, 1950, and letter from R. Kelly to Louis W. Spolyer, February 14, 1950, Monsanto Archives). In 1953, a Monsanto industrial hygienist, Elmer Wheeler, expressed concern about the possibility of painters using new latex paints that contained PCBs as plasticizers. Painters had been sickened when these paints were “applied in confined or unventilated areas, particularly if the paints might be used on heated surfaces” (memo, E. Wheeler to E. Mather, “Aroclors: Toxicity,” September 1, 1953, Monsanto Archives). More information about PCB leaks came from industries in which PCBs were used. In 1954, Meigs and colleagues published an article in the Journal of the American Medical Association documenting skin eruptions among chemical workers:

Seven cases of mild to moderate chloracne of the face and head occurred among 14 chemical operators exposed from 5 to 19 months intermittently to small concentrations of the vapors of a chlorinated diphenyl Arochlor [sic]: Leakage of these vapors from a heat exchange system occurred chiefly outdoors, but chloracne was observed among men working inside the adjacent building. ¹³

In 1955, more reports of end users of PCBs becoming ill as a result of exposure to the chemical came out: “There has been some trouble in the use of Aroclors as heat-exchange fluids, but this is always associated with poorly designed and leaking equipment. In one case, three people suffered liver damage in about a week’s exposure” (W. B. Brown to Dr J. W. Barrett, August 19, 1955, Monsanto Archives). That same year, the Bureau of Medicine of the Navy questioned the use of PCBs in their submarines as hydraulic fluids because of concern about the effects that the chemicals might have on board the vessels, which could be submerged for weeks at a time. When Pydraul 150, a PCB product, was promoted by Monsanto for use as a hydraulic fluid in submarine periscope housings, according to internal correspondence between the company and Navy officials, “submarine crews have had to wear rubber suits and dress up like men from Mars when handling or working with” it (letter, E. Wheeler to J. Treon, August 29, 1955, Monsanto Archives). Further evidence of end users being harmed by PCBs was documented in 1957, when the Bucyrus Erie Company in Milwaukee, Wisconsin, which used Pydraul 150 in its hydraulic system, noted that because of “numerous hose and piping failures,” “pydraul [was] sprayed over our workmen and in a number of cases workmen’s eyes have been seriously burned” (letter from R. Davis to J. Arbogast, March 21, 1957, Monsanto Archives).

By the late 1950s and early 1960s, the concern broadened. PCBs could be a hazard not only to workers in the chemical plants or to end users in other facilities but also to consumers who might be exposed to them inadvertently. For example, one Monsanto employee warned that because PCBs were being marketed “to increase the insecticidal life of Lindane [an insecticide]” there could be problems because of the possibility that such a combination could be used

on food or feed crops.…We repeatedly find that users of formulations prepared for a specific use will apply the material for other uses. In other words, even though Monsanto may encourage the use of Aroclor in pesticide formulations for non-agricultural use you can rest assured that some of it will be used on agricultural commodities. (memo, L. W. Sherwood to Benignus, “Aroclor Use to Increase the Insecticidal Life of Lindane,” August 30, 1957, Monsanto Archives)

In 1960, the Frito Company wrote about a problem with its cooking fat. “He said they believe they found chlorine in their cooking fat and suspected a leak in their heat exchanger” (memo, R. Davis to File, “The Frito Company,” October 18, 1960, Monsanto Archives). This and other examples of leaks in heat-exchange systems that used PCBs raised the possibility that foods might be contaminated with PCBs, which was another way that people could absorb the chemical. Other leaks and spills were noted in the 1960s and beyond (letter from R. Kelly to J. P. Allen, Hexagon Laboratories, February 17, 1961, Monsanto Archives; letter from R. Davis to J. M. Kerr, Rockwell Manufacturing Company, May 14, 1965; memo, R. Kelly to R. Davis, January 25, 1965; memo, J. H. Schuch to File, “Aroclor 4465,” December 10, 1968, all from Monsanto Archives).

In 1966, concern arose about the pollution coming from the PCB plant in Anniston, Alabama, that resulted in the death of fish. In late 1966, Sören Jensen and colleagues in Sweden documented the presence of PCBs in wildlife and humans, even in places where PCBs had never been used. ¹⁴ By late 1967, evidence showed just how widespread PCB pollution had become. In the late 1960s, what had first been identified as a threat to workers in the chemical industry, then to end users in other industrial plants, and then to an unsuspecting naval personnel, and finally to Europeans far removed from the United States, blossomed into a broader concern about the American public. In 1968, Robert Risebrough, a researcher at the University of California, Berkeley, and colleagues published an article in Nature that documented broad swaths of California’s coastline, bird population, and fish that were contaminated with PCBs. ¹⁵ After this article was published, numerous other investigators began identifying PCBs in the fish in the Great Lakes, rivers, and streams around the country (letter, D. Ferguson to Monsanto, November 2, 1966, Monsanto Archives). It was apparent that PCBs were entering the ecosystem through a host of routes: waste waters, disposal and dumping, and air. “Unfortunately it appears that significant air pollution can occur…[because of the] burning of NCR paper [National Cash Register carbonless carbon paper] [or] other Aroclor containing materials” (memo, E. S. Tucker to W. R. Richard, “Aroclor—Wildlife: Incineration of NCR Paper,” March 4, 1969, Monsanto Archives). Then, in 1968, an outbreak of poisoning in Japan by what was identified as PCB-contaminated rice oil, affecting more than 1000 people (the Yusho incident), brought PCB contamination of the human food chain to worldwide attention. ¹⁶

In April 1969, Robert Metcalf, a consultant for Monsanto, reported that tens of millions of pounds per year of PCBs were used for plasticizers, hydraulic fluids, adhesives, and carbon paper, and “a very substantial percentage must escape into the environment as waste; at least 10 million lbs/yr may become environmental contaminants.” He urged prompt action: “PCB effects on environmental quality is sufficiently substantial, widespread and alarming to require immediate corrective action on the part of Monsanto” (unpublished report, R. L. Metcalf, “Report and Comments on Meeting on Chlorinated Biphenyls in the Environment at Industrial Biotest Laboratories, Chicago,” March 21, 1969, April 2, 1969, Monsanto Archives).

Several months later, in September 1969, an internal Monsanto memorandum revealed another source of pollution: the PCBs in the drums that the company shipped to customers. Monsanto official W. A. Kuhn wrote the following:

We ship about 20 [million] pounds/year in drums. Whatever a customer leaves in a drum eventually ends up in a natural stream of some sort and the total could be as high as 200 000 pounds/year.…Even this is a small loss compared to the several million pounds per year thrown to the atmosphere via incineration of carbonless carbon paper by innumerable users. (W. A. Kuhn to H. S. Bergen and W. R. Richard, September 16, 1969, Monsanto Archives)

Monsanto, the sole producer of PCBs, began to understand the depths of its problem. The company organized an ad hoc committee, consisting of 5 leading Monsanto officials, in August 1969 to figure out how to address both the ecological and public health problem as well as the public relations disaster that the company saw looming as more investigators, politicians, and lawyers pointed to the company as the source of this worldwide contaminant. One participant took notes at a meeting of the ad hoc committee on August 25, at which the committee members discussed alternatives: “1. Go out of business. 2. Sell the hell out of them as long as we can and do nothing else.…3. Try to stay in business in controlled applications—control contamination levels” (minutes of meeting, “PCB Committee—August 25—[19]69” Monsanto Archives). At another meeting of the committee, in September 1969, it was acknowledged that “in one application alone (highway paints) one million lbs/year are used. Through abrasion and leaching we can assume that nearly all of this Aroclor winds up in the environment” (minutes of Aroclor “Ad Hoc Committee,” September 5, 1969, Monsanto Archives). In early October 1969, a first draft of a confidential report by the ad hoc committee was distributed internally. This draft made clear that the committee understood the extent of the environmental problem that Monsanto had created during the several decades it had produced and sold PCBs.

The committee believes there is little probability that any action that can be taken will prevent the growing incrimination of specific PCBs (the higher chlorinated—e.g., Aroclors 1254 and 1260) as nearly global environmental contaminants of human food (particularly fish), the killing of some marine species (shrimp), and the possible extinction of several species of fish eating birds. Secondly, the committee believes that there is no practical course of action that can so effectively police the uses of these products as to prevent completely some environmental contamination. There are, however, a number of actions which must be undertaken to prolong the manufacture, sale, and use of these particular Aroclors as well as to protect the continued use of other members of the Aroclor series. (“Report of Aroclor Ad Hoc Committee,” October 2, 1969, Monsanto Archives) ³

In the quarterly report of the Monsanto Medical Department, Dr Emmet Kelly, the company’s medical director, provided what he considered a “summary of most significant developments” of the period July through September 1969: “Polychlorobiphenyls (Aroclors) publicity become nationwide and portentious [sic].” He noted that it was “likely…that it will be found impossible to prevent losses to the environment of Aroclor 1254 and 1260 in some customer applications…” (E. Kelly, Medical Department, “Quarterly Report,” Ca. October 1969, Monsanto Archives). The report was marked, “Please destroy this Report when you are finished with it [emphasis in the original].”

Ironically, Monsanto had initiated a project in 1938 that could have provided evidence for the persistence of PCBs in the environment, but no follow-up was performed. At that time, Monsanto started a termite soil poison test in Gainesville, Florida, that placed various Aroclors in 80 of the 540 holes dug into the soil. The company even “proposed that this test area be examined annually and that records be made at such time relative to the individual conditions of each [2-by-4] wood specimen” that was placed in each hole (Memo, Ira Hatfield, “Termite soil poison tests—Gainesville, Florida,” June 28, 1939, Monsanto Archives). But according to Monsanto’s records, it does not seem that these plots were examined again until 1969.

During the next several years, more evidence accumulated about the presence and effects of PCBs in the environment. In 1971, the United States created an Interdepartmental Task Force on PCBs. In May 1972, the task force issued a report, “Polychlorinated Biphenyls and the Environment,” which stated that: “1) PCBs should be restricted to essential or non-replaceable uses which involve minimal direct human exposure since they can have adverse effects on human health. 2) PCBs have been used so widely over such a long period that they are ubiquitous.” The report listed the various ways that PCBs got into the environment: open burning or incomplete incineration; vaporization from paints, coatings, plastics, and others; municipal and some industrial sewers; accidental spills or improper waste disposal practices; formerly, direct application to the environment as ingredients of pesticides or as carriers for pesticides; dumping of sewage sludge, municipal and industrial solid waste, and dredge spoil at sea; sewage sludge disposed of on land; and migration from surface coatings (eg, paint) and packaging materials into foods and feeds. ¹⁷

By the early 1970s, the fears first noted in the 1930s had come full circle. A host of chlorinated hydrocarbons had been identified as persistent dangers to the public and to the environment and were rapidly being pulled from the commercial marketplace. The growing environmental movement had slowly destroyed the public’s view of these chemicals and threatened the reputations of their producers. Although in 1969 Monsanto said “there [were] no restrictions which control the current uses of our Aroclors or PCBs” (unpublished “Report of Aroclor ‘Ad Hoc Committee’ [second draft],” October 15, 1969, Monsanto Archives), by the mid-1970s, Russel E. Train, administrator of the US Environmental Protection Agency, was calling for a voluntary ban on PCBs. In large part because of concerns about PCBs, Congress passed the Toxic Substances Control Act in late 1976, which banned the manufacture or distribution of PCBs, although the law did not take effect until 1979. ^18,19

In many ways, the history of chlorinated hydrocarbons parallels the history of other known toxins that companies introduced into the environment during the 20th century in the United States. Similar to the producers of asbestos and lead products, the producers of chlorinated hydrocarbons expanded production dramatically in the second half of the 20th century. This expansion took place despite the growing body of scientific and observational data, much of which were produced by the companies themselves, which showed that their products were dangerous. As other historians have shown in analyses of these toxic substances, companies often did not act on information that threatened the market for their products. ^{20 -25}

Notwithstanding the fact that congressional hearings identified the dangers of the widespread use of DDT and other chlorinated hydrocarbons as pesticides in the early 1950s, it would not be until the mid- to late-1960s that the pressure from environmental scientists, journalists, and politicians linked to a broader environmental movement would force the issue of possible harm to nature and people onto the public agenda. Early studies showed that PCBs were an acute threat to the factory workers that produced them, and the impact of PCBs on the environment would quickly emerge in the 1950s. However, it would not be until the late 1970s that PCBs would finally be banned. It took a broad environmental movement and the creation of federal agencies dedicated to protecting workers, communities, and the environment to end the use of DDT, PCBs, lead in gasoline and paint, and asbestos in the United States and other industrialized countries.