Why were pops singled out for regulation by the international community?

According to the European Commission, the POP (Persistent Organic Pollutant) are chemicals that should be eliminated. The international community called for an action to reduce and eliminate POP. To arrive at this solution having two agreements. First is The Protocol to the regional UNECE Convention on Long-Range Transboundary Air Pollution (CLRTAP) on POPs called for open signatures in June 1998 and entered into force on 23 October 2003. Second is The global Stockholm Convention on POPs, opened for signatures in May 2001 and entered into force on 17 May 2004