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The late 1890s and early part of  the 20th century were characterized by rapid industrialization, with a  huge growth in low-wage factory jobs. These factories were incredibly  unsafe: employees working with dangerous chemicals could expect  to come home covered in them, and people were even locked  into their places of work.

And these jobs came with illnesses  and conditions that were considered unavoidable occupational risks. But if you wanted your children  to eat, you’d take those risks. Enter Dr.

Alice Hamilton, who asked:  how can we mitigate those risks to keep people safe and healthy at work? Alice Hamilton was born in  1869, which you may recognize as a time with very few women  represented in medicine. But Alice had made up her  mind when she was a teenager that that’s what she wanted to do.

So after taking lots of extra  anatomy classes, and sweet-talking her father into letting her go, she enrolled at. University of Michigan’s  medical school and got her MD. After doing her residencies, she  decided that she’d rather do research than open a practice, so she went  to Germany to study bacteriology.

And there, she had to agree to  make herself invisible in order to attend lectures, a process involving  a lot of sneaking into seats that were carefully hidden in  the backs of lecture halls. And after coming back to the US,  she lived and worked at Chicago’s. Hull-House, a so-called “social  settlement” where recent immigrants could receive services like  healthcare and language classes.

Alice ended up treating many  of the members of the community for injuries and conditions  they sustained on the job. She credited her time at Hull-House  as one of the main reasons she started researching what were  then called industrial diseases. So she turned her medical and  scientific training to the issue of making these workplaces  safer, starting with her own.

In 1905, she published a paper on  the transmission of scarlet fever and similar diseases in hospital  settings, and made some findings that are especially salient today. She had a group of patients  with scarlet fever cough, cry, and breathe over a set of petri  dishes, and then incubated the samples to see if  Streptococcus pyogenes, the microbe that causes scarlet fever, was present. Which it absolutely was.

And she found that the best way  to block it was simply to cover the mouth and nose, because  the vector for the disease appeared to be saliva and respiratory droplets. So she recommended that  surgeons always wear masks when performing surgery, because  you could have scarlet fever, but have yet to show symptoms. This was a really important move  in occupational safety for hospital workers, but the results held  true for any disease where respiratory droplets can be a  vector, making these findings monumental for public health.

Among other research, her work  is why mask-wearing caught on as a way to reduce the spread  of disease: first during the 1918 Spanish flu, and more  recently with things like SARS,. MERS, and…well, COVID-19. While some of her early work was  studying respiratory diseases,.

Alice would really make a  name for herself when it came to industrial toxins. She was hired to investigate lead,  first by the State of Illinois and later by the US Department of Labor. Because lead was cheap and  really easy to work with, it was used in just about everything,  like pipes, foil, and paint.

And the thing is, people  already knew lead was toxic; they just didn’t understand how. We now believe that lead is poisonous  because the body mistakes it for calcium, which the body uses  for bones and teeth, and in lots of cell-signalling pathways controlling  muscle and neuron function. This means that lead  concentrates in bones and teeth, in nerves, and in the brain.

And when lead deposits in bone  rather than immediately gumming up the works in your brain and  muscles, then you’ve got a super fun lead reserve in your body  that can be slowly released long after exposure. So at the time Alice Hamilton  was beginning her research, you’d see a wide variety of symptoms  in folks who worked with lead, and the onset and development  of those symptoms didn’t always coincide with exposure. Which made it difficult to  pin down lead as the source of these illnesses -- and  the owners of these factories were perfectly happy with that,  blaming symptoms on alcohol use or poor hygiene.

But Dr. Hamilton proved them  both wrong... and very liable. In order to gather her data,  she basically had to become an investigative reporter.

She’d slip into factories  without the owners’ permission, because the owners regularly  lied about how much lead they were using and how they used it. She’d also take factory workers  and union leaders out for beers so they could speak freely, and  had workers sneak her samples of materials so she could test them for lead. And she discovered over 70  industrial processes through which workers were being poisoned and killed, leading to major safety overhauls in  the lead industry, as well as the replacement of lead in  stuff like paint and foil.

Her work made her the expert  in occupational health, so when Harvard began their  industrial hygiene program, they hired her on as an assistant professor. She never got tenure -- you can  maybe guess why -- but she did negotiate for half of every year  off to continue her field work. And it’s because of her  efforts that the United States has organizations like OSHA and  NIOSH, which create guidelines for workplace safety and continue to  research workplace health hazards.

So thanks to Alice Hamilton’s  ingenious scientific mind and unparalleled awesomeness,  the world is a much safer place. Thanks for watching this episode of SciShow, and thanks to our patrons for  helping to make it happen. We really enjoy being able  to tell stories about awesome overlooked figures from history  like this, and it’s your support that makes it possible.

So if  you’d like to get involved, check out patreon.com/scishow. [♪ OUTRO].