Contrary to popular media there is no simple answer to this question. While the website The Endocrine Disruption Exchange (TDEX) offers a comprehensive excel spreadsheet of the products, chemicals, and their health effects, it fails to mention the variety of factors that are important in determining what will make the identified chemical toxic to the public.
Will There Be Wide Spread Health Problems?
There is a general assumption that because of the nature or the toxicity of the chemicals used in natural gas development there will be widespread health issues. To explain why this assumption is wrong, we need to first define the word "toxicity."
Toxicity is defined by the Agency of Toxic Substances and Disease Registry (a federal agency) as the “degree to which a substance is poisonous or can cause injury.” The key word here is “degree,” it is the reason why the answer is simple not. The degree is the “how toxic.”
No Exposure means No Toxicity
How often and how you are exposed and how much were you exposed to? The “dose-response relationship” is important when determining whether a chemical will be toxic. A one-time large exposure, a small exposure repeated over and over; there are many different combinations of how much and how often that go in determining toxicity. However, if the chemicals are contained before, during and after hydraulic fracturing, there will be no exposure; therefore no toxic effects.
Toxicity depends on the concentration at point of contact;
How does the chemical enter into the body? The chemical first has to enter the body. There are three major routes; through an oral route- where people may eat or drink a contaminated product; inhalation route- is when the chemical enters through our lungs and dermal route- is where chemical is absorbed through the skin. Again, toxicity varies greatly on how the chemical enters the body. Some chemicals that enter orally may not be as toxic as they would be if they were inhaled. Some chemicals undergo processes in the body that make them less toxic or in some cases vice versa. However, if the chemicals do not enter your body, then you will not be affected.
Other factors. There are also other factors that influence the toxicity of a chemical. These include nutrition, state of health, individual susceptibility, chemical combinations, adaptability, and age.
When we talk about the toxicity of chemicals, we have to talk about the many different factors which vary from case to case.
So, which chemical is the most toxic?
To answer this question and ones above, a Risk Assessment is performed. It is a multiple step process that sets up for the evaluation as to whether a chemical can be used safely, its use needs to be mitigated or removed from use. The best answer is... it depends.