In linguistics and grammar, a pronoun (abbreviated PRO) is a word that substitutes for a noun or noun phrase. It is a particular case of a pro-form.
Some of the most significant toxic effects associated with substances used or emitted in plastic production include: 13. 1  Benzene (PET, PVC, LDPE, PP): known human carcinogen, workplace exposure depresses the nervous system. 2  Chromium oxide (HDPE, LDPE): suspected carcinogen, damaging to the liver and nervous system.ome of the most significant toxic effects associated with substances used or emitted in plastic production include: 13. 1  Benzene (PET, PVC, LDPE, PP): known human carcinogen, workplace exposure depresses the nervous system. 2  Chromium oxide (HDPE, LDPE): suspected carcinogen, damaging to the liver and nervous system.
Benzene and its derivatives are mainly used in synthetic organic chemistry. The main source of polynuclear aromatic compounds is coal tar. For example, naphthalene is the largest single constituent (6 - 10%) of coal tar.ince six pi electrons are delocalized over whole ring, therefore the cyclically conjugated double bonds represents by a circle and the carbon-carbon bond length becomes equal. This structure of benzene is called as resonance hybrid of benzene and generally used to represents the benzenemolecule.