As science continues to progress, we continue learning what types of chemicals and elements are harmful to humans.

Looking back, it’s crazy to see some of the things that we used in everyday items that would never be acceptable today given what we’ve learned about them. Here are just a few:

Asbestos

Large-scale use of asbestos, naturally occurring silicate minerals, began in the mid-19th century. The material was typically used in insulation due to its sound absorption, tensile strength, resistance to fire and heat, and its affordability.

The first documented death related to asbestos was in 1906 — its negative effects had been recorded much earlier than that but not thoroughly understood at the time. Today, more than 10,000 people in the U.S. still die each year from asbestos, now known to cause a type of cancer called mesothelioma.

Radium

During the early 1900s, it was all the rage to paint wristwatch dials with radium so that they would glow in the dark, constantly illuminating the time. The clocks themselves contained very little of the radioactive element and were typically covered in glass, so they weren’t too dangerous on their own.

The main problem with this practice was that the women who painted the watch dials with radium, later called the “Radium Girls,” typically licked their paintbrushes to keep a sharp point and even painted their nails and faces with it. The company behind this kept the effects of radium secret from the women, even telling them it was healthy for them.

Later in life, the women began showing signs of anemia, necrosis of the jaw, and bone fractures. Within a few years, 50 women had died as a result of radiation poisoning.

Scheele’s Green and Paris Green

Before the nontoxic green paints and dyes we have today, there was Scheele’s Green — a bright green substance created to give life to everything from walls to dresses to candy. It sure was pretty to look at, but at the end of the day, Scheele’s Green was an arsenic compound.

People exposed to the substance were poisoned, and people began realizing that Scheele’s Green was the cause so they created Paris Green — another arsenic compound. It wasn’t until people again starting falling ill again that scientists began discovering that it was the arsenic that made them ill.

Lead

Throughout history and all over the world, lead has been used in a lot of different applications — paint, gasoline, piping, bullets, sailboat keels, windows, and so much more (but, surprisingly, not pencils — that is a misconception).

Though lead was believed to be harmful much earlier, it wasn’t until the late 19th and early 20th centuries that it was understood that lead caused mental disorders, gout, blindness, and more. After extensive research, steps were taken in the western world to limit the everyday contact that people have with lead.

Mercury

For some time, many believed that mercury had healing effects. In fact, the first emperor of China died after drinking a mixture of powdered jade and mercury which was meant to provide eternal life.

In more modern times, mercury has been used in thermometers and as a gas in fluorescent lamps. But today, we know that mercury and most of its compounds are extremely toxic and can be absorbed through the skin and mucous membranes or inhaled if exposed to mercury vapor.