For babies and young children, breathing particulate air pollution is extremely harmful to their health and development, as it can cause permanent damage to brain tissue and lungs, according to the report copied to the Ghana News Agency.

UNICEF warns that since air pollution was not monitored in Africa as other parts of the world, "we are not only potentially underestimating the severity of the impact– we might also be underestimating its scope".

It said in Europe and North America 72 per cent of children live where air pollution was measured, 43 per cent in Asia, and 25 per cent in South America.

The report noted that air pollution was a growing challenge for Africa and that air pollution impacted ecosystems – vital to livelihoods and health – as well as food crops.

A recent study in the report estimated the economic cost of premature deaths from outdoor air pollution across Africa to be $215bn.

Deaths from outdoor air pollution in Africa have increased to 57 per cent over nearly three decades, from 164,000 in 1990 to 258,000 in 2017.

It noted that without ground-level monitoring stations that reliably measure air quality, Africa's children were increasingly at risk of unwittingly breathing air that was toxic for their health and brain development with the ability to devise effective responses greatly compromised.

Henrietta Fore, Executive Director, UNICEF, said "Air pollution is a silent killer of children. And in Africa especially, we know the problem is severe, we just don't know how severe".

"Reducing children's exposure to pollutants – and therefore reducing the damage to children's health and early brain development – begins with a reliable understanding of the quality of air they are breathing in the first place."

Silent Suffocation in Africa measures the population of children living near reliable ground-level air quality monitoring stations.

The report also offers guidance on different types of ground-level monitoring systems from regulatory-grade monitors to low-cost sensors.

It said ultrafine pollution particles were so small they could enter the blood stream, travel to the brain, and damage the blood-brain barrier, which can cause neuro-inflammation.

The report said other types of pollution particles, such as polycyclic aromatic hydrocarbons, can damage areas in the brain that were critical in helping neurons communicate, the foundation for children's learning and development.

It said to understand the full extent of the problem, UNICEF urged governments to put in place permanent and high-quality ground-level monitoring stations as public goods.

The report said when combined with satellite imagery, such stations would form the backbone of a system that would help improve the reliability of less precise monitoring stations that capture variations across cities.

It said reliable ground level data helped to better capture the daily – even hourly – fluctuations in air quality.

The report said monitoring also helped to identify sources of pollution, shaping public health policy, and informing action and interventions that targeted the most affected.

It said UNICEF urged governments to invest in renewable sources of energy to replace fossil fuel combustion; provide affordable access to public transport; increase green spaces in urban areas; provide cleaner cooking and heating solutions; and create better waste management options to prevent open burning of harmful chemicals.

It called for prevention of children's exposure to air pollution, including creating smart urban planning, so that major sources of pollution were not located near schools, clinics or hospitals; and minimize exposure in the home.

It insisted on the need to improve children's overall health to improve their resilience through the prevention and treatment of pneumonia, as well as the promotion of exclusive breastfeeding and good nutrition.

"A young child's brain is especially vulnerable because it can be damaged by a smaller dosage of toxic chemicals, children breathe more rapidly, and physical defenses and immunities are not fully developed," said Fore.

"If toxic air is stunting our children's development, it is stunting our societies' development as well. All governments should take the necessary steps to make sure we know exactly what we are putting into the air and what it is doing to our children's health and well-being."