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Air pollution hot spots link to congenital birth anomaly – SAMRC study

Pregnant women living in air pollution hot spots risk bearing a child with a congenital birth anomaly – specifically orofacial cleft lip and palate (CLP), according a study by the South African Medical Research Council (SAMRC), in partnership with surgeons, researchers and Operation Smile.

The research was presented last month at the Climate Child Health Series: The Impact of Climate Change on Newborn Health Outcomes, held online by the US Child Health Task Force and UN International Children’s Emergency Fund, reports The Citizen.

The SAMRC said the study draws together cases of patients with CLP from 2006 to 2020. Drawing from two databases, 2 515 cases were studied about air pollution, assessed at the mothers’ residence.

“The research identifies an association between the increasing trend in CLP and a mother’s exposure during early pregnancy to particulate matter (PM) air pollution, PM10 and PM2.5,” SAMRC said.

The experts defined CLP as birth anomalies that typically affect a baby’s lip or mouth and nose because these parts do not form properly during pregnancy.

“This may happen during weeks four and seven of pregnancy. When a baby is developing, body tissue and special cells from each side of the head join to make the face.”

SAMRC said there were several possible causes of CLP, including genes; what the woman eats and drinks; whether she smokes; uses a certain type of medication during pregnancy; and the environment in which she lives.

Dr Caradee Wright, chief specialist scientist at the SAMRC’s Environment and Health Research Unit, said: “Air pollution levels are known to be high in South Africa, coming from coal-fired power stations, traffic, domestic fuel burning, mining, industry and other sources.

“We wanted to explore whether a mother’s exposure to air pollution affected her baby’s cleft lip and palate risk.”

Wright said the CLP birth hot spot clusters were found in district municipalities in Gauteng, Limpopo, North West, Mpumalanga and Free State.


The findings emphasise the need for more stringent air quality management to protect the health of unborn children. Researchers have also called on the National Ambient Air Quality Standards and Air Pollution Priority Areas to strictly manage the air quality.

“Information needs to be provided to mothers regarding the risks air pollution poses to their unborn child, especially in very early pregnancy. It’s important that if someone wants to fall pregnant, they try to limit air pollution exposure.”

CLP patients also experience a higher mortality risk and deal with the adverse effects of physical challenges like speech impediments, physical deficiencies in appearance, and psychosocial issues.

“Added to the difficulties confronted by children with CLP are nutritional problems caused by the inability to consume food. The malnutrition that is a result of CLP is not properly recorded because death certificates list these as (just) malnutrition.”

The study found that an approach with multiple disciplines collaborating and sharing data on all maternal information and pollutant volumes in all provinces might prevent CLP.

Study details

The Risk of Orofacial Cleft Lip/Palate Due to Maternal Ambient Air Pollution Exposure: A Call for Further Research in South Africa

Caradee Wright, Thandi Kapwata, Bianca Wernecke, Helen Malherbe, Kurt-W Bütow, Natasha Naidoo, Rebecca Garland, Anzel de Lange, Gareth Murray; OPERATION SMILE.

Published in The Annals of Global Health on 23 January 2023


Despite being underreported, orofacial cleft lip/palate (CLP) remains in the top five of South Africa's most common congenital disorders. Maternal air pollution exposure has been associated with CLP in neonates. South Africa has high air pollution levels due to domestic burning practices, coal-fired power plants, mining, industry, and traffic pollution, among other sources. We investigated air pollutant levels in geographic locations of CLP cases.

In a retrospective case series study (2006-2020) from a combined dataset by a Gauteng surgeon and South African Operation Smile, the maternal address at pregnancy was obtained for 2,515 CLP cases. Data from the South African Air Quality Information System was used to calculate annual averages of particulate matter (PM) concentrations of particles < 10 µm (PM10) and < 2.5 µm (PM2.5). Correlation analysis determined the relationship between average PM2.5/PM10 concentrations and CLP birth prevalence. Hotspot analysis was done using the Average Nearest Neighbour tool in ArcGIS.

Correlation analysis showed an increasing trend of CLP birth prevalence to PM10 (CC = 0.61, 95% CI = 0.38-0.77, p < 0.001) and PM2.5 (CC = 0.63, 95% CI = 0.42-0.77, p < 0.001). Hot spot analysis revealed that areas with higher concentrations of PM10 and PM2.5 had a higher proclivity for maternal residence (z-score = -68.2, p < 0.001). CLP birth prevalence hotspot clusters were identified in district municipalities in the provinces of Gauteng, Limpopo, North-West, Mpumalanga, and Free State. KwaZulu-Natal and Eastern Cape had lower PM10 and PM2.5 concentrations and were cold spot clusters.

Maternal exposure to air pollution is known to impact the foetal environment and increase CLP risk. We discovered enough evidence of an effect to warrant further investigation. We advocate for a concerted effort by the government, physicians, researchers, non-government organisations working with CLP patients, and others to collect quality data on all maternal information and pollutant levels in all provinces of South Africa. Collaboration and data sharing for additional research will help us better understand the impact of air pollution on CLP in South Africa.


Annals of Global Health article – The Risk of Orofacial Cleft Lip/Palate Due to Maternal Ambient Air Pollution Exposure: A Call for Further Research in South Africa (Open access)


The Citizen article – Pregnancy: Air pollution may lead to congenital birth anomaly (Restricted access)


See more from MedicalBrief archives:


Air pollution as bad as smoking for miscarriage risk


Sooty air pollution particles reaching the placenta


Air pollution during foetal life linked to brain abnormalities


One in six people dying prematurely from air pollution







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