ABSTRACT
To determine how polluted the environment is or how much people or other organisms and communities are affected, you need an appropriate comparator. This is not a problem with experimental studies which include controls, but in the field, you will frequently have difficulty determining what comparisons are appropriate. Several years ago, I reviewed a study of effects of mine drainage on a lake, led by a respected consultant. He could not find uncontaminated sites with conditions equivalent to the contaminated areas and admitted that there was no real reference site. Never-the-less, he published an assessment which concluded that there were no effects based on comparison of contaminated and less contaminated sites that had different types of habitat. While I sympathized with his difficulty, I would not use his results. This chapters explains and describes background and reference points, and the importance of both in an environmental assessment.
