Heat pumps require a refrigerant to work correctly. The most commonly used refrigerant used in heat pumps was chlorofluorocarbons (CFCs). This changed in August 1987 with the Montreal Protocol which banned or restricted the manufacture of CFCs. In the 1990s, hydrofluorocarbons (HFCs) were developed to replace CFCs as they have minimal ozone depletion potential. However, they still pose a serious risk to the environment as they have strong greenhouse gas effects as stated in the Kyoto Protocol.
Heat pumps have another impact in that they produce noise since the require moving parts to work. In air source heat pumps an external unit containing moving mechanical parts (usually fans) produces noise. There are no established standards for noise barriers or noise protection. However, the United States only allows heat pumps to produce 55 decibels of noise during the day (about the noise level of background conversation in a restaurant) and 45 decibels at night (about the noise level of calls). This is to protect us from any adverse health effects and to protect the welfare of residential areas.
Heat Pump: https://en.wikipedia.org/wiki/Heat_pump
Kyoto Protocol: https://en.wikipedia.org/wiki/Kyoto_Protocol
Montreal Protocol: https://en.wikipedia.org/wiki/Montreal_Protocol