Toxicology and Risk Assessment

EPA Process Evaluation Carbon Dioxide (CO2) is the primary greenhouse gas emitted through human activities of electricity, transportation, and industry that accounted for 84% of all U.S. greenhouse gas emissions from human activity in 2010 (Greenhouse Emissions: Carbon Dioxide Emissions). CO2 has a natural presence through the atmosphere, oceans, soil, plants, and animals. Human activity is altering the carbon cycle by influencing the ability of natural sinks, such as forests, to remove CO2 from the atmosphere.

Because of this situation, the Environmental Protection Agency (EPA) takes measures by testing processes and public policies to reduce the influence of the human activity in reduction of the CO2 in the atmosphere. The toxicity assessment is the tool EPA uses to determine what levels are dangerous or could cause harm to the environment or human health.

The basic objective of the toxicity assessment is to identify adverse effects of a chemical and how appearance of the effects depends on the exposure level, route of exposure, and duration of exposure (Toxicity Assessment). The assessment is divided into two parts consisting of non-cancer effects and cancer effects. Threshold doses are determined by estimating toxicological data from previous studies. The thresholds are determined to lie between the highest dost that does not produce effect and the lowest dose that does produce effect.

The non-cancer evaluations are based on a Reference Dose (RfD), which is an estimate of daily exposure that is likely without effects, instead of the threshold doses. The cancer effects are assessed in two components. The first component is a qualitative evaluate of the weight of evidence that the chemical does not cause cancer. The second part is done for chemicals that are determined to cause cancer and quantification is performed to determine the number of cancers the chemical causes in animals and humans.

This is a toxicity that describes the toxicity potency of the chemical. A carcinogen risk assessment is provided for each chemical. For CO2, it was determined that small doses of 10 parts per trillion are safe. Large amounts of 1,000 or more per trillion are harmful and produce human health effects. EPA has released a new rule that requires soot pollution maximum to be reduced by 20% in efforts to reduce illness and save lives (Press, 2012).

The issue of soot pollution has been battled over by environmental and business groups in regards to protecting public health or causing job losses and harming economic growth. The American Petroleum Institute claimed there had been no scientific evidence to warrant the ruling. They also referred to forthcoming environmental regulations. Soot pollution contains CO2 as well as five other contaminants. It is made up of microscopic materials released from smokestacks, diesel trucks, wood-burning stoves, and other sources that contribute to haze. All U.S.

counties are required to be in compliance with the new ruling by 2020 when stronger enforcement of the rule is expected.