Environmental impact of menstrual cups

Impact of the production
Menstrual cups were first patented in 1937 by Leon Chalmers. In the early 2000’s, companies began producing menstrual cups with more durable materials. DivaCups are made of medical grade silicone, Keepers are gum rubber based; DivaCups are also designed to be more comfortable and easier to use. Companies promote menstrual cups as a better alternative to pads and tampons by marketing them as more practical, cheaper, and eco-friendly.
Silicone based cups
Injection molding of liquid silicone rubber is the method used in order to produce the menstrual cups and to have the bell-shaped cup. In order to get liquid silicon, there are a few steps that have to be done beforehand. Silicon (production of 850,000 t/y) is made from silica sand, which is reduced at high temperature in an electric furnace at <1,400 °C. The reducing agent is coke:
The production of silicon releases carbon monoxide, which is highly toxic and takes part in ground level ozone formation:
The extraction of silicon from silica sand impacts the environment with the production of carbon monoxide which plays a key role in the green house effect.
The mining of the material also have a big impact on the environment.
Impact of silica mining
The first step to production is of course the obtaining of the raw material. For this product it is the mining of silica. Silica mineral is a major constituent of the lithosphere. A study conducted in the Shankargarh region shows that silica mining can lead to land deterioration, loss of biodiversity, and ground water depletion. The pollution from suspended particulate matter can also accumulate on tree leaves and disturb photosynthesis.
This reaction generates chlorosilanes, which react with polar agent. In presence of H2O, the chlorosilanes are transformed into siloxanes via an hydrolisis reaction. More precisely, dimethylsiloxanes will be the monomer to the silicone polymer. The polimerisation process is catalised via acids and bases to give the following structure.
Vulcanization of silicone rubber
Polymerization produces a liquid polymer which is then shaped into the bell-shaped cup. The rubber receives its practical properties via a process called vulcanization, which cross-links the linear chains between themselves. After vulcanization, the resulting material is more flexible and stable.
Economic impact
One of the highlighted assets of the menstrual cup is its reusability. According to manufacturers, a cup can last a decade if used properly. Considering that a woman in a developed country would buy an average of $60 of pads and tampons year and that menstrual cycle repeats for 35 to 40 years, this adds up to a net expense of $2,400 on pads and tampons during a lifetime. Considering that the potential life of a menstrual cup is 10 years and that it costs around 30 to 40 dollars, the expenses invested in menstrual management is divided by a factor of 10.
Disposal of the menstrual cups
Each year, an estimated 20 billion pads and tampons are discarded in North America. They typically end up in landfills or are incinerated, which can have a great impact on the environment. Most of the pads and tampons are made of cotton and plastic. Plastic takes about 50 or more years and cotton starts degrading after 90 days if it’s composted.
The fact that the menstrual cup is reusable greatly decreases the amount of waste generated from menstrual cycles as there is no daily waste and the amount of discarded packaging decreases as well. After their life span is over, the silicon cups are put in landfills or incinerated. When put into landfills, the polymer can be degraded according to the following reaction.
Degradation of the polymer
As described above, silicone rubber is degraded into the monomer then into inorganic silicate which have been reported to have no environmental impact. Depending on the type of soil, the rate of degradation will be influenced, the degradation rate can go from 27 µg/day to 1299 µg/day. There is also a generation of CO<sub>2</sub> which will be released into the atmosphere and contribute to global warming.
Additives present in the cups
Most of the cups produced don't usually have any other additives to them, except for the colored cups. However, the coloring used is reported to be safe and approved by FDA for medical use and food coloring.

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