Often the question is how you can decide whether a chemical affects human health. The problem of human cells is that these cells loose some properties if they have been isolated from the tissue. Considering this the single cell organism Tetrahymena pyriformis was chosen. It is comparable in sensitiveness and responsiveness to human tissue cells, is an organism and independent from tissue and is a model for human respiratory epithelium-cell functionalities. The effects of extracts bioaerosols (mould spores) and associated mycotoxins (gliotoxin and penicilic acid) are of special interest. The following end points have been investigated: viability (cell count), energy levels (adenosine-5’-triphosphate content), and cell respiration (oxygen consumption). Effects on cell proliferation and on physiological processes are suitable indicators for the different impact of chemicals. T. pyriformis is a suitable organism to study effects of ubiquitous chemicals.