Here are entered works on the assessment of human or animal exposure to noxious agents by measuring the toxic agent and/or metabolite in biological specimens, e.g. blood, hair, etc.
Here are entered works on the process of taking up free nitrogen, either by microorganisms or by technical or natural processes. Works on the formation of nitrites and nitrates in soil, sewage sludge, etc. from other nitrogenous compounds by microorganisms are entered under Nitrification.
Here are entered works on the interrelationships of organisms and their environment, including other organisms. Works on the composite of physical, biological, and social sciences concerned with the conditions of the environment and their effects are entered under Environmental sciences. Works on the relationship of humans to the natural environment are entered under Human ecology. Works on the relationship of humans to their sociocultural environment are entered under Social ecology. --subdivision Environmental aspects under subjects, e.g. Agricultural chemicals--Environmental aspects; Nuclear power plants--Environmental aspects; and headings beginning with the word Ecological
