Environmental toxins linked to heart defects

Children’s congenital heart defects may be associated with their mothers’ exposure to specific mixtures of environmental toxins during pregnancy, according to research presented at the American Heart Association’s Scientific Sessions 2013.

Congenital heart defects occur when the heart or blood vessels near the heart don’t develop normally before birth. Defects may be caused by chromosomal abnormalities, but the cause is unknown in most cases.

Researchers examined patterns of congenital heart defects incidence and presence of environmental toxicants in Alberta, Canada. The ongoing research seeks to determine if pregnant women’s proximity to organic compounds and metals emitted in the air impacts the risk of heart defects in their children.

“Although still in the early stage, this research suggests some chemical emissions - particularly, industrial air emissions - may be linked to heart abnormalities that develop while the heart is forming in the womb,” said lead researcher Deliwe P. Ngwezi, M.D., a Ph.D., student and research fellow in pediatric cardiology at the University of Alberta in Canada.

The study is based on congenital heart defects diagnosed in 2004-11 and chemical emissions recorded by a Canadian agency tracking pollutants.

Researchers looked at three chemical categories, but only one group showed a strong correlation with rates of congenital heart defects. According to Ngwezi, the group of chemicals consists of a mixture of organic compounds and metals namely: benzene, butadiene, carbon disulphide, chloroform, ethylene oxide, hexachlorobenzene, tetrachloroethane, methanol, sulphur dioxide, toluene, lead, mercury and cadmium.

Environmental toxins linked to heart defects Congenital heart defect rates have gradually decreased in Canada since 2006, which is about the time the government tightened regulations to reduce industrial air emissions, Ngwezi said. The heart defect decreases were mainly associated with heart defects resulting in holes between the upper and lower heart chambers (septal defects) and malformations of the cardiac outflow tracts (conotruncal defects), according to Ngwezi.

“For now, consumers and healthcare providers should be educated about the potential toll of pollutants on the developing heart,” she said. “As we have observed in the preliminary results, when the emissions decrease, the rates of congenital heart defects also decrease.” This study, she said, should draw attention to the increasing evidence about the impact of environmental pollution on birth defects. Limitations of the study include that researchers’ observations were made at a group level, not according to individual risk and the self-reported industry data which is monitored and collected annually by government, according to Ngwezi.

Congenital heart disease (CHD) can describe a number of different problems affecting the heart. It is the most common type of birth defect. Congenital heart disease causes more deaths in the first year of life than any other birth defects.

Congenital heart disease is often divided into two types: cyanotic (blue skin color caused by a lack of oxygen) and non-cyanotic. The following lists cover the most common congenital heart diseases:


  Ebstein’s anomaly
  Hypoplastic left heart
  Pulmonary atresia
  Tetralogy of Fallot
  Total anomalous pulmonary venous return
  Transposition of the great vessels
  Tricuspid atresia
  Truncus arteriosus  


  Aortic stenosis
  Atrial septal defect (ASD)
  Atrioventricular canal (endocardial cushion defect)
  Coarctation of the aorta
  Patent ductus arteriosus (PDA)
  Pulmonic stenosis
  Ventricular septal defect (VSD) 

These problems may occur alone or together. Most children with congenital heart disease do not have other types of birth defects. However, heart defects can be part of genetic and chromosome syndromes. Some of these syndromes may be passed down through families.


Co-authors are Lisa K. Hornberger, M.D.; Brad Saretsky, B.Sc.; Sujata Chandra, M.D., M.Sc.; Deborah Fruitman, M.D., F.R.C.P.C.; and Alvaro Osornio-Vargas, M.D., Ph.D. Author disclosures are on the abstract.

Environmental toxins linked to heart defects The study was funded by the Women and Children’s Health Research Institute, University of Alberta; Hamilton-Naki Foundation of South Africa; and an Emerging Research Team Grant from the University of Alberta’s Faculty of Medicine and Dentistry and Alberta Health Services.

Learn more about Congenital Heart Defects.

In the United States

At Birth

  Congenital heart defects are the most common type of birth defect in the United States, affecting nearly 1% of - or about 40,000 - births per year.

  The prevalence of some congenital heart defects, especially mild types, is increasing, while the prevalence of other types has remained stable. The most common type of heart defect is Ventricular septal defect.

Among Children and Adults

  __ Currently, no population-based tracking program exists to collect data on children and adults with congenital hearts defects. Therefore, other methods have been used to estimate the number of people with these defects among this growing population.

    |__ One study estimated that, in 2002, there were 650,000 to 1.3 million adults living with a congenital heart defect. To estimate this, researchers used prevalence at birth and estimated the number of individuals expected to survive, with and without treatment.

    |__ Another study estimated that, in 2000, about 850,000 adults were living with a congenital heart defect, with about 80,000 of these individuals living with a severe heart defect. To obtain this estimate, researchers used data from administrative health care databases in an area where health care was universal.

  __ Based on those studies, there likely are nearly 1 million adults in the United States living with a congenital heart defect.


Statements and conclusions of study authors that are presented at American Heart Association scientific meetings are solely those of the study authors and do not necessarily reflect association policy or position. The association makes no representation or warranty as to their accuracy or reliability. The association receives funding primarily from individuals; foundations and corporations (including pharmaceutical, device manufacturers and other companies) also make donations and fund specific association programs and events. The association has strict policies to prevent these relationships from influencing the science content.

Note: Actual presentation time is from 3 p.m. CT/4 p.m. ET Sunday, Nov. 17, 2013.

Downloadable video/audio interviews, B-roll, animation and images related to this news release are on the right column of the release link at http://newsroom.heart.org/news/environmental-toxins-linked-to-heart-defects?preview=176456a4352eb666d9efa2edb9f0edf2. Video clips with researchers/authors of the studies will be added to the release link after embargo.


Bridgette McNeill
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American Heart Association

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