Mozambique is going through a post-election period marked by deaths, injuries and the use of police force to disperse crowds. On several occasions the police fired tear gas bullets into the crowds, sometimes even into homes.

According to the Center for Public Integrity (CIP), the tear gas used by the police was expired. The capsules collected in the cities of Maputo and Matola had an expiry date of July 2014. Under these conditions it is considered "hazardous waste".

"Regular and prolonged exposure to gas causes adverse effects on public health and the environment. The effects are exacerbated when humans and the environment are exposed to the gas out of time," CIP said in a publication.

There is also the risk of death for anyone who has been exposed to tear gas, whether on or off the clock.

Mental health can also suffer, with cases of panic, post-traumatic stress, depression, anxiety and sleep disturbances.

The NGO points out that the chemical properties of tear gas can damage the environment and kill wildlife species.