In 1871, Washington Roebling, the chief engineer on the Brooklyn Bridge, went down into one of the bridge’s caissons. He wanted to see with his own eyes the conditions his workers faced every day. When he came back up, he had a very severe form of the illness that the men called caisson disease, and it left him paralyzed for the rest of his life.
Roebling was not the first person to suffer from the disease, and he would not be the last. The illness had travelled with a new way of building, from the coal fields of France to the great rivers of the United States. In the 1870s, nobody understood what caused it.
The word caisson comes from the French word for “box”. A caisson was a huge chamber filled with compressed air. Builders used it to construct the piers and foundations that hold a bridge firmly in place in a river. Men dug at the bottom of the chamber, and the pressure of the air kept the water from coming in. This method made building quicker and cheaper, but it had a cost that was not obvious at first. In the caissons of this period, men worked at pressures of up to 55 pounds per square inch above normal air pressure, and the disease was common among them. Today the condition is known as decompression sickness. When the pressure around a person drops quickly, nitrogen that has dissolved in the blood and body tissues can form bubbles. These bubbles cause pain in the joints, difficulty breathing, itching, confusion and seizures.
Roebling had started work in May 1870 on a bridge 1,600 feet long that would link Manhattan with Brooklyn. Its caissons were bigger than any that had been built before. Each one covered 16,000 square feet, which made them three times the size of the caissons used for the bridge that was being built at the same time across the Mississippi at St. Louis. The idea for the bridge had come from his father, John A. Roebling, who died while the work was still at an early stage.
The first person to use a pressurized chamber for work was Charles-Jean Triger, a French civil engineer and geologist. In 1840 he wanted to mine coal in the Loire Valley. He pumped compressed air into a chamber that was open at the bottom, and the air pushed the water out. This allowed miners to dig below the level of the groundwater. The chamber was in use for about two weeks, and the men worked shifts of seven to ten hours. Before every shift, Triger went down through the airlock himself to check the air and the conditions. His chamber caused the first injuries from compressed air that we know of.
Later, Triger employed two doctors, B. Pol and T. J. J. Watelle. They examined and treated 64 workers on a project at Douchy, in northern France, which was reportedly carried out at three and a half times normal air pressure. They noted that many workers suffered from breathlessness, pain in the joints and muscles, and itching when they left the caisson. Pol became ill himself. He recovered only after a night of terrible chest pain, paralysis and vomiting. The two doctors were right to connect how serious the illness was with how fast the pressure was released. However, they were wrong to believe that it was caused by a lack of oxygen in the blood. Even so, in 1854 they became the first to suggest that putting a patient back under pressure could be a treatment.
At St. Louis, the bridge was designed by James Eads. Its caissons were sunk toward the solid rock that lay 100 feet below the surface of the Mississippi. By the time they reached 60 feet, the men were complaining of pain in their joints, partial paralysis in their legs, headaches and itching. Many of them came out of the caissons bent forward in pain. This position reminded people of the Grecian Bend, a way of standing that was fashionable among women at the time. For that reason, people said the sick men had “the bends”. When one caisson was close to its deepest point, 93 feet, six men died. By the end of the project, almost a quarter of all the workers had suffered from the disease. Thirty were taken to hospital, 13 died, and two were disabled for life.
In 1870 Alphonse Jaminet, a local doctor, set up a small hospital on a barge next to the building site, with beds and blankets. It was one of the first medical clinics at a workplace in America. He made the workers stay with him for “at least one hour after work, while drinking three-quarters of a pint of strong beef tea.” Jaminet went down into the caisson himself. When he came back up, he had pain in his ears and felt extremely cold. Because of this, he told the men to wear warm clothes while the pressure was being released. He wrongly believed that the bends came from putting the men under pressure too quickly. Still, he set fixed speeds for going into the caissons and for coming out of them. Compared with modern practice, his decompression was very fast. But simply controlling its speed was a step toward preventing the disease. He published a description of his experience in 1871.
At Brooklyn, the man responsible for the workers’ health was Andrew H. Smith, a doctor who specialized in diseases of the throat. He recorded 86 cases of caisson disease, with joint pain, headaches, itching, shortness of breath and paralysis. He treated the men with the drugs morphine or atropine. However, since nobody yet knew the real cause, there was little he could do to stop the illness from happening. He did notice that most of the men who became ill were overweight, and that every man who died was described as “obese”. This observation was later used to support the idea that being very overweight increases the risk. Smith published his report in 1873. In 2024, a review in the journal Laryngoscope concluded that Smith was mistaken about how the disease worked. Even so, it found, his strict rules and his quick action made it possible to finish the bridge’s stone towers.
At the same time, Roebling was facing the limits of his own design. As the digging went on, he became worried about the growing number of injuries and deaths. In the end he stopped work at 78 feet. This was short of the 100 feet that people thought were needed to reach solid rock. He went against the advice he received and built the Manhattan tower on sand. The writer Joel Cook later said that Roebling was an invalid, unable to lead a normal active life, for years after he became ill.
Another person took over part of the job of dealing with the world outside. In May 1883, a newspaper in Sacramento reported on a visit to New York. Representatives of mills that hoped to win contracts for the bridge had travelled there to ask Colonel Roebling for advice. According to the newspaper, they were very surprised when Mrs. Roebling sat down with them. Using her knowledge of engineering, she helped them with their designs and solved their problems. The bridge opened in the same month.
Abram S. Hewitt was chosen to speak for the city of New York, and he gave a speech about the bridge. It was printed in the magazine Popular Science Monthly in July 1883. He said that “the name of Mrs. Emily Warren Roebling will thus be inseparably associated with all that is admirable in human nature.” He also talked about what the bridge had cost the Roebling family: “Death, indeed, was the fate of its great projector, and dread disease the heritage of the greater engineer who has brought it to completion.”
The explanation finally came from Paul Bert, a French physiologist, a scientist who studies how the body works. In 1870 he was carrying out many experiments with air pressure. He showed that the disease was caused by decompression that happened too quickly. He also noticed that the symptoms often appeared ten to thirty minutes later. He recommended three things: slower decompression, pure oxygen for mild symptoms, and putting the patient back under pressure at once in cases of paralysis. These three practices are still the basis of treatment today. In 1908, experiments by J. S. Haldane led to the advice that decompression should be done in stages.
None of this knowledge arrived in time to help the men working in the East River. Hewitt pointed out that even the electric light had been perfected too late to be used in the caissons. He asked his listeners to remember not only the engineers but also “the unnamed men by whose unflinching courage, in the depths of the caissons,” the bridge had been built.