The Protocol on Heavy Metals, a protocol to the Convention on Long-Range Transboundary Air Pollution, was adopted in Aarhus, Denmark, in 1998. As of 2004, it had 36 signatories. As of 2016, it had 35 signatories and 33 parties, with no country having become a signatory since 1998.[1] The protocol addresses the reduction of cadmium, lead and mercury emissions in the interests of environmental protection.[2] Amendments to the Protocol were agreed in 2012[3] to introduce more stringent emission limits[4] but are not yet in force.