Industrial toxicology

Alice Hamilton and the Development of Occupational Medicine

Industrial toxicology

Alice Hamilton’s formal investigations into the connection between occupation and disease began in 1910 when she was appointed by Illinois Governor Charles Deneen to head a survey on industrial illness in Illinois. Little was known about industrial toxicology, so the members of the commission had to figure out what trades to explore and to devise a methodology. They decided to concentrate on occupational poisons in trades known to be dangerous. In addition to managing the survey, Hamilton studied lead, the most widely used industrial poison. Others reported on arsenic, zinc smelting, brass manufacturing, turpentine, and carbon monoxide.

Hamilton and her assistants visited factories, read hospital records, and interviewed labor leaders and druggists to uncover instances of lead poisoning. Hamilton wrote in her autobiography, "I was put on the trail of new lead trades." She discovered more than seventy industrial processes in which workers were exposed to lead poisoning. In addition to the more readily known industries where lead exposure was high, industries such as painting, enamelware, and pottery, Hamilton found some less obvious ones, including polishing cut glass and wrapping cigars in "tinfoil," actually made from lead.

She proudly relates one example in her autobiography, Exploring the Dangerous Trades, to demonstrate the difficulty in tracking down instances of lead poisoning and the unexpected industries where it occurred. In one hospital she found a Polish worker suffering from colic and double wrist drop. He said he worked in a sanitary-ware factory, applying enamel to bathtubs. The existing literature made no mention of lead in the paint used to make bathtubs and the managers of the factory, after assuring Hamilton that lead was not used, let her inspect the workroom. Puzzled, she tracked down the victim who told her she witnessed only the final touching up of the bathtubs. The real work occurred at another factory where "enameling means sprinkling a finely ground enamel over a red-hot tub where it melts and flows over the surface." A specimen a worker gave her contained as much as 20 percent soluble lead. "Thus I nailed down the fact," Hamilton wrote, "that sanitary-ware enameling was a dangerous lead trade in the United States."

The Illinois report on industrial disease proved the connection between occupation and illness. As a result, the Illinois legislature in 1911 passed an occupational disease law requiring employers to implement safety procedures limiting workers’ exposure to dangerous chemicals, to provide monthly medical examinations for workers in dangerous trades, and to report illnesses to the Department of Factory Inspection, which had prosecutorial authority. Hamilton’s work in Illinois caught the attention of Charles Neill, the Commissioner of Labor (the United States Bureau of Labor was a part of the Department of Commerce until 1913). Neill asked her to do nationally what she had done in Illinois, first in the lead trades, then in other poisonous occupations. Hamilton described the limitations under which she worked: "I had, as a Federal agent, no right to enter any establishment – that must depend on the courtesy of the employer. I must discover for myself where the plants were, and the method of investigation to be followed. The time devoted to each survey, that and all else, was left to my discretion. Nobody would keep tabs on me, I should not even receive a salary; only when the report was ready for publication would the government buy it from me at a price to be decided on."

Hamilton accepted Neill’s offer "and never went back to the laboratory." Convinced that she would never be anything but "a fourth-rate bacteriologist" and that she had "no scientific imagination," Hamilton never doubted her decision to focus on industrial toxicology, which she described as "scientific only in part, but human and practical in great measure." Moreover, the job meant she could continue to live at Hull-House, which remained her base even as she traveled the country investigating the dangerous trades.

Hamilton began her work for the federal government by investigating white lead, commonly used as a paint pigment. Building on what she learned while conducting the Illinois survey, Hamilton looked for lead dust and lead fumes since she was convinced the danger for workers came from breathing air laden with the toxic chemical, and not from ingesting lead. Already Hamilton employed the techniques of "shoe-leather epidemiology" that marked all her probes: the careful and extensive use of hospital records to demonstrate the connection between specific illnesses and occupations, and the thorough investigation of factories to learn which industrial processes used dangerous chemicals. Hamilton could not force her way into factories, but could only request entry. Few denied her, and once inside she looked for evidence of lead dust and fumes and inquired about the degree of sickness.

Hamilton’s investigation of lead poisoning occurred before reliable diagnostic tests existed, so she relied on a self-imposed rigid standard. "I would not accept a case as positive," she wrote, "unless there was a clear ‘lead line’… a deposit of black lead sulphide in the cells of the lining of the mouth, usually clearest on the gum along the margin of the front teeth, and it is caused by the action of sulphureted hydrogen on the lead in these cells, the sulphureted hydrogen coming from the decaying of protein in the food in the mouth." This was the standard she employed as she probed lead poisoning among workers in smelting, enameling, painting, and printing.

Hamilton was not content to merely reveal the extent of lead poisoning in American industry. Armed with the information she gathered, Hamilton personally tried to persuade factory owners and managers to remedy dangerous conditions. A lifelong dread of conflict made this difficult for Hamilton. But, perhaps owing to her Victorian upbringing, Hamilton was convinced that people of goodwill, once aware of the facts, would do the right thing. She wrote of an instance of this in her autobiography when she confronted Edward Cornish of the National Lead Company and told him that his workers were being poisoned. Cornish was "both indignant and incredulous" at first, but when she presented him with twenty-two cases of severe lead poisoning he reformed his plants by instituting dust and fume prevention by techniques never before used. Hamilton also convinced Cornish to employ doctors to conduct weekly inspections of his workers.

During the First World War Hamilton conducted studies on the dangers of toxic chemicals in the burgeoning war industries. Because of the need for explosives, factories sprang up to produce TNT, picric acid, mercury fulminate, and many other substances. Her reports on the dangers in war industries led to the adoption of many safety procedures, and she later claimed, with some irony given her anti-war activism, that the war years helped make industrial toxicology a respectable field of study. There was also some irony in her reluctance to overtly protest the war since she wanted to continue working for the Department of Labor.

Her biographer, Barbara Sicherman writes in Alice Hamilton: A Life in Letters: "By 1915 Alice Hamilton had become the foremost American authority on lead poisoning and one of a handful of prominent specialists in industrial disease." She may not have been the first or the only person studying occupational medicine, but she was probably its only fulltime practitioner. So when the Harvard Medical School began a program of industrial hygiene, Hamilton was the obvious choice for appointment as assistant professor of industrial medicine. In 1922, she moved to the School of Public Health, launched that year by Harvard. She accepted the appointment at Harvard on condition that she teach only one semester a year so that she could continue her field studies. In 1925, she wrote the first text in the field, Industrial Poisons in the United States, and in 1934 she published Industrial Toxicology. Over the years, she studied aniline dye, carbon monoxide, mercury, benzene, and other toxic chemicals, continuing to issue reports for the Department of Labor on the dangerous trades.

After her retirement in 1935, Hamilton conducted a study of the poisons used in making viscose rayon. This new industry used two dangerous chemicals: carbon disulfide, which poisoned the central nervous system and led to mental disease, loss of vision, and paralysis; and hydrogen sulfide, a powerful asphyxiating toxin. Hamilton first encountered carbon disulfide in 1914 when she studied rubber making, and she later reported its use in the manufacture of viscose rayon. Despite its wide use in Europe, carbon disulfide received little attention in the United States, but Hamilton became worried in the 1930s when she received reports of serious illnesses among viscose rayon workers. She persuaded the Department of Labor to investigate and to appoint her chief medical consultant. The results of the study were published in Occupational Poisoning in the Viscose Rayon Industry. It was Hamilton’s last investigation, and she was able to write in her autobiography that "control of this dangerous trade was slow in coming but when it came it was astonishingly rapid and complete." Viscose rayon workers, like thousands of workers in other dangerous trades, could thank Alice Hamilton for helping to control chemical toxins in the workplace.

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