The tests required to assess the health of the soil and water are easy enough to implement and include in any investigation. It is however hard to find the environmental factors that had led to the pollutants in the soil and water. This is because unless the source of the contaminants is found directly, there must be some sort of conjecture as to what the source is. Therefore it is extremely difficult to pinpoint the causation in the case of environmental pollutants and even more difficult to find what factor is at fault. Fajersztajin noted that even if measurement of one carcinogenic compound is conducted daily with a large amount of data, it is hard to eliminate the fact that other carcinogenic compounds or other factors entirely may be at fault.
Detecting pollutants in the atmosphere can be a fairly straight-forward process. It does however take some hypothesizing as to figuring out how many people have been exposed to the various pollutants. In order to find out how many people are exposed data must be gathered to include: the source of the pollutants, the distance from the sources to population centers, the distance from the sources to resources such as water, agriculture, and the geographical characteristics of the region. With this data and the concentration of pollutants, one can find out how many people are exposed and then create estimates of how many people are exposed in similar areas. This is problematic as any model created from these locations is bound to be error prone as all factors cannot be considered and the models will usually be inaccurate as even geographically similar regions can be vastly different.
One of the most difficult things for environmental scientists to do is link air pollution with the degradation of human health. It is similarly related to government agencies in the past attempting to link smoking with lung cancer. Although one can argue that there certainly is a correlation between smokers and lung cancer, it falls back onto the old saying: correlation does not mean causation. Air pollution and lung cancer is the same except it is even more difficult to link the two because of the vast variance of cities. Not only are the physical features of cities different, but also the behavior of its inhabitants. Some city dwellers may choose to use gas masks while others do not mind the mild irritation due to air pollution. These two populations even if they are similar in size and composition may not be compared equally.
Shayler, H. (2009, April 15). Soil Testing and Interpreting Results. Retrieved February 1, 2016, from http://cwmi.css.cornell.edu/guidetosoil.pdf
Kessler, R. (2014, July 1). Air Pollution's Impact on Cancer Is "Grossly Underestimated" Retrieved February 01, 2016, from http://www.scientificamerican.com/article/air-pollution-s-impact-on-cancer-is-grossly-underestimated/