Pollution worldwide is increasing, and along with that, causing more health issues for populations around the globe. Side-effects of exposure are many, varied and often devastating, and while major attempts are being made to reduce emissions and clean up the air that we breathe, the world still has a long way to go, writes MedicalBrief.
We need to do much more, much faster, according to Elaine Mulcahy, in an opinion piece in the British Medical Journal, who writes that outdoor air pollution accounted for 2.9m deaths globally in 2000. Less than 20 years later, in 2019, that figure had risen to 4.5m, she says. The air we breathe is causing one in every six of us to die prematurely, and little is being done about it. The problem is getting worse.
The 2017 Lancet Commission on pollution and health was a stark warning of the global burden of pollution on health and economic development. It found pollution was responsible for some 9m deaths and economic losses totalling US $4.6 trillion (6.2% of global economic output) in 2015. It noted the deep inequity of pollution, with low-income and middle-income countries carrying the greatest burden of deaths and economic losses.
Since then, we have gone backwards. The updated report published in May 2022, based on data from 2019, shows little progress is being made.
Since 2000, deaths caused by ambient air pollution and toxic chemical pollution have increased, writes Mulcahy, driven by industrialisation, uncontrolled urbanisation, population growth, fossil fuel combustion, and an absence of adequate international chemical policy.
And despite declines in deaths from household air and water pollution, most notably in Africa where improvements in water supply, sanitation, antibiotics, treatments and cleaner fuels have contributed to reduced mortality, this has been offset by increases in ambient air pollution and toxic chemical pollution.
The number of deaths caused by pollution is on a par with smoking, and globally, its impact on health is greater than war, terrorism, malaria, HIV, tuberculosis, drugs, and alcohol. Yet, the report says that despite growing evidence for pollution contributions to non-communicable disease morbidity and mortality, international and national NCD control programmes focus almost exclusively on behavioural and metabolic risk factors such as tobacco use, exercise, and obesity, while ignoring pollution.
Mulcahy writes that pollution is a global problem requiring a global effort. Pollutants can travel long distances in wind, water, in the food chain and consumer products, and while wealthier countries displace much of their pollution footprint overseas, lower-income countries are experiencing increasing levels of pollution domestically.
To date, the international funding response to tackle pollution has been insufficient. The Lancet Commission reports that official development assistance (ODA) contributions to international conventions and frameworks concerning pollutants and chemicals amounted to just US $860m in 2016-18, inadequate for the scale of a problem that accounts for global economic losses equivalent to 6.2% of GDP (US $4.5 trillion) annually.
Air pollution accounts for 82% of the total economic losses and is also the major cause of death, accounting for 6.5m deaths every year. Outdoor air pollution accounts for 4.5m of these deaths. Pollutants including methane, black carbon, and hydrofluorocarbons (HFCs) are a major contributing factor to both outdoor air pollution and climate warming.
In fact, the first years of life have been identified in a recent study in Barcelona as the most sensitive period of exposure to air pollution.
It showed that higher exposure to air pollution has been linked to higher functional brain connectivity among several brain regions in pre-adolescents, while exposure to traffic noise has not, according to the research, led by by the Barcelona Institute for Global Health (ISGlobal), an institution supported by “La Caixa” Foundation.
Traffic-related air pollution and noise are affecting an increasing number of people worldwide, and “we already know children are particularly vulnerable to the effect of these exposures, because of their immature metabolism and developing brain”, said ISGlobal researcher and senior author Mónica Guxens.
The study was published in the journal Environment International.
Several studies by Guxens and others have found an association between exposure to traffic-related air pollution during early childhood and alterations in the brain structure.
In this study, the research team used magnetic resonance imaging (MRI) to explore whether higher exposure to air pollution or noise could also be associated with possible alterations in brain connectivity (i.e. the way in which different brain regions interact).
They used data from 2,197 children from the Generation R Study, born between April 2002 and January 2006 and living in Rotterdam, the Netherlands. Using land use models, they estimated levels of nitrogen oxides (NOx and NO2) and particulate matter (PM) at the participants’ homes at different time periods: during pregnancy, from birth to three years, from three to six years, and from six years of age to the age at which the MRI scan was performed.
Noise levels from traffic were estimated using existing noise maps. Between nine and 12 years of age, the participants were invited to undergo an MRI scan in the resting state (i.e. with no external stimuli).
The findings show that higher exposures to NO2 and PM2.5 absorbance (an indicator of black carbon particles) from birth to three years, and to NOx from three to six years of age, were associated with higher functional brain connectivity among several brain regions in the pre-adolescents.
The associations were identified in brain areas predominantly involved in two networks that have strongly opposing functions: the task negative (or “default-mode”) network tends to be activated in resting conditions and the task positive network tends to be activated during tasks that demand attention.
“We still have to understand the consequences of this increased activity of both networks in resting conditions, but for now we can say that the brain connectivity in children exposed to higher levels of air pollution is different from what we would expect,” says Laura Pérez-Crespo, first author of the study.
The period from birth to three years was the one with the highest susceptibility to air pollution, and black carbon was the pollutant most associated with brain connectivity changes.
As the authors noted, the main source of black carbon and nitrogen oxide gases in European cities are diesel vehicles.
Meanwhile, in South Africa, Environmental Minister Barbara Creecy is attempting to appeal a judgment by the Gauteng High Court (Pretoria) that ordered her to implement air quality regulations for the Mpumalanga Highveld.
According to a Beeld report, Creecy argued that the judgment offended the principles of separation of powers.
Judge Colleen Collins found the minister was unduly slack with promulgating regulations and action plans to improve air quality. The court therefore ordered her to include appropriate fines for offenders in regulations, to appoint properly trained enforcement officers, upgrade monitoring stations in Mpumalanga and make available online all data on air quality. Creecy wants to appeal some aspects of the judgment and order, saying a court cannot order a minister to formulate and implement regulations as this falls within the discretion of the executive.
The order was also vague and not enforceable, Creecy argued, adding that her appeal was not aimed at delaying the implementation of an action plan and regulations, but to get clarity on the legal issues. She is already dealing with the action plan and regulations while the appeal is pending.
The environmental organisations that brought the original application – groundWork and the Vukani Environmental Justice Alliance Movement in Action – expressed disappointment at the appeal.
Exposure to traffic-related air pollution and noise during pregnancy and childhood, and functional brain connectivity in preadolescents.
Laura Pérez-Crespo, Michelle S.W. Kusters, Mónica López-Vicente, Małgorzata J. Lubczyńska, Maria Foraster, Tonya White, Gerard Hoek, Henning Tiemeier, Ryan L. Muetzel, Mònica Guxens.
Published in Environment International on 16 June 2022
The amount of people affected by traffic-related air pollution and noise is continuously increasing, but limited research has been conducted on the association between these environmental exposures and functional brain connectivity in children.
This exploratory study aimed to analyse the associations between the exposure to traffic-related air pollution and noise during pregnancy and childhood, and functional brain connectivity amongst a wide-swath of brain areas in preadolescents from 9 to 12 years of age.
We used data of 2,197 children from the Generation R Study. Land use regression models were applied to estimate nitrogen oxides and particulate matter levels at participant’s homes for several time periods: pregnancy, birth to 3 years, 3 to 6 years, and 6 years of age to the age at magnetic resonance imaging (MRI) assessment. Existing noise maps were used to estimate road traffic noise exposure at participant’s homes for the same time periods. Resting-state functional MRI was obtained at 9–12 years of age. Pair-wise correlation coefficients of the blood-oxygen-level-dependent signals between 380 brain areas were calculated. Linear regressions were run and corrected for multiple testing.
Preadolescents exposed to higher levels of NO2, NOx, and PM2.5 absorbance, from birth to 3 years, and from 3 to 6 years of age showed higher correlation coefficients among several brain regions (e.g. from 0.16 to 0.19 higher correlation coefficient related to PM2.5 absorbance exposure, depending on the brain connection). Overall, most identified associations were between brain regions of the task positive and task negative networks, and were mainly inter-network (20 of 26). Slightly more than half of the connections were intra-hemispheric (14 of 26), predominantly in the right hemisphere. Road traffic noise was not associated with functional brain connectivity.
This exploratory study found that exposure to traffic-related air pollution during the first years of life was related to higher functional brain connectivity predominantly in brain areas located in the task positive and task negative networks, in preadolescents from 9 to 12 years of age. These results could be an indicator of differential functional connectivity in children exposed to higher levels of air pollution.
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