During my Master's degree at Columbia University, I studied dioxin emissions in the United states.
Dioxins are a group of related chemical compounds. They are persistent environmental pollutants of major concern due to their high toxicity. Dioxins are created by a wide range of processes, including industrial processes and natural processes, and are found throughout the world.
The Environmental Protection Agency conducted a national inventory of dioxin emissions for the years 1987, 1995, and 2000. Part of research involved performing a new inventory for the year 2012, and updating the older values using more recent data.
This post shows the results of this research, and showcases several visualizations.
In order to assess the overall toxicity of a specific dioxin mixture, each compound is assigned a Toxic Equivalency Factor (TEF) compared to the most toxic dioxin compound. This allows us to measure dioxin amounts with a single scale: toxic equivalent (TEQ). Unless specified, all values below are in grams TEQ.
All of the images are togglable:
- Click on a thumbnail to see full sized image.
- Click on a full sized image to see the thumbnail.
The first way see the data is in table form.
First, we see that dioxin emissions have fallen pretty significantly since 1987 - just over 75%. Most of that decrease is due to a decrease in the waste category. In particular:
- Waste to energy dioxin emissions fell from 9500 g TEQ to 3 g TEQ - over 99.9% reduction. This is primarily due to the fact that now air pollution controls are implemented to reduce dioxin emissions. The amount of waste undergoing thermal treatment has not changed significantly.
- Medical waste incineration emissions fell from 2700 g TEQ to 7 g TEQ. This decrease is due to both much better controls and a large decrease in the amount of medical waste incinerated (from 1.4 million metric tons down to 0.137 million metric tons).
Treemaps are a way of visualizing hierarchical data. These treemaps were created in R using the treemap package. Each rectangle represents a dioxin emissions source, and the area is proportional to the emissions value. However, the different treemaps are not to scale - i.e. the total emissions in 2012 was lower than 1987 but here the treemaps are the same size.