Page 10 - Pim Wassenaar
P. 10

Chapter 1

                 1.1 Chemical universe

                 We are surrounded [...]. They are in front of us, behind us, and we are flanked
                                             on both sides […].

                 Two quotes by Lewis Burwell Puller, who was a US marine from 1918-1955, inspired me
                 [1]. Although not thinking of military action, but talking about chemicals. Chemicals are
                 everywhere. We see, feel, inhale, drink and eat them, and there is no way to avoid them all.

                 Chemicals are involved in most of our activities during daily life and fulfil a fundamental role
                 in our society. Since the 19  century, the chemical industry evolved rapidly, including the
                 development of synthetic fertilizers, plastics, dyes, surfactants and pharmaceuticals [2]. These
                 advancements significantly influenced and formed modern society as we know it.

                 The indispensability of chemicals is particularly evident from the large number of over 350,000
                 chemicals and chemical mixtures that are registered worldwide for production and use [3].
                 These chemicals, that represent the so-called chemical universe, can be divided in several
                 categories based on various aspects including the type of substance, chemical structure, and
                 environmental source or type of application (see Textbox A).

                  Textbox A: Characterizing the chemical universe

                  The chemical universe, as illustrated in Figure A.1, can be categorized based on various
                  aspects including the type of substance, chemical structure and environmental source or
                  type of application.

                  Type of substance
                  In general, three types of substances can be identified [8]. The first two types are the mono-
                  and multi-constituent substances. Like the names suggest, both types contain one or several
                  main constituents (i.e. structures/components) and potentially some impurities that make
                  up the composition. These two categories are also described as well-defined substances, as
                  the composition is (or can be) well characterized. The third type concerns UVCB substances,
                  which  stands  for  substance  of  Unknown  or  Variable  composition,  Complex  reaction
                  products or Biological materials. These substances contain many different constituents
                  of which some can be (partially) unknown and/or the exact composition can be variable
                  or difficult to predict. Besides these substance types, other categories can be defined, like
                  polymers and fibers (including plastics and nanomaterials).

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