Ammonium is one of the specific components of fine particulate matter (PM2.5), that has been linked to a higher risk of death compared to other chemicals found in it, according to a new study in the journal Epidemiology.

Particulate matter is one of the most dangerous air pollutants – a complex mixture of extremely small particles and liquid droplets which can be directly emitted from natural sources, such as forest fires, or when gases emitted from power plants, industries and automobiles react in the air.

PM2.5 is airborne particulate matter smaller than 2.5 µm in diameter. It is usually believed the black carbon part of PM2.5 (mainly stemming from motorised vehicles) was the most harmful one. However, the team’s analysis of data in 210 cities across 16 countries from 1999-2017 found human health risks from air pollution vary depending on the proportion of different components in PM2.5.

One of the most dangerous components is ammonium (NH4+), originating mostly from fertiliser use and livestock. The risk of excess mortality from PM2.5 roughly increased from 0.6% to 1% when the proportion of ammonium increased from 1% to 20% in the mix1.

Cities with a larger concentration of ammonium in the mix, including Japanese cities Aikita, Aomori, Sendai, and Canadian cities London Ontario and Sarnia were associated with higher health risks. Specific action aimed at the agricultural and farming sectors may speed up the reduction of the negative health impacts of air pollution.

Release date: 16 December 2021
Source: London School of Hygiene & Tropical Medicine

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