The secondary research process involved comprehensive analysis of regulatory chemical databases, industry trade publications, petrochemical market intelligence reports, and authoritative polymer industry organizations. Key sources included the US Environmental Protection Agency (EPA), European Chemicals Agency (ECHA), Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH), Food and Drug Administration (FDA) (for food-contact applications), Occupational Safety and Health Administration (OSHA), American Chemistry Council (ACC), Plastics Industry Association (PLASTICS), European Plastics Association (EuPC), China Petroleum and Chemical Industry Federation (CPCIF), Japan Plastics Industry Federation (JPIF), Indian Chemical Council (ICC), National Institute of Standards and Technology (NIST), International Agency for Research on Cancer (IARC), National Center for Biotechnology Information (NCBI) (for toxicity studies), World Trade Organization (WTO) trade statistics, UN Comtrade Database, International Monetary Fund (IMF) commodity price data, US Census Bureau (chemical trade data), Eurostat (EU chemicals production), and national chemical ministry reports from key petrochemical markets. These sources were utilized to collect production capacity data, regulatory restriction updates, styrene monomer price trends, recycling technology developments, sustainability mandate impacts, and competitive landscape analysis for general purpose polystyrene, high impact polystyrene, expanded polystyrene foam, and extruded polystyrene insulation products.