Growing Knowledge: How Health Canada is going the distance to study human impacts of chemical exposure

This article is the first in a five-part series about chemical exposure in pregnancy and childhood.

 

Since 2007, a team of scientists at Health Canada, have been working on an ambitious, multi-year study of environmental chemicals and their possible health effects on mothers, starting during pregnancy and throughout childhood development, from infancy to adolescence.

 

The first of its kind in Canada, the Maternal-Infant Research on Environmental Chemicals (MIREC) has since been the source of many major scientific discoveries that are now helping to protect mothers and their children from chemical exposure risks.

“Before MIREC, very few studies had been done on pregnancy and exposure to chemicals. In fact, they had mostly been done on adult men,” says Dr. Tye Arbuckle, Co-Principal Investigator of MIREC. “Kids are not little adults! They are more susceptible to chemical exposure, starting from the moment they are conceived.”

“We had a vision of following children through time, to examine the chemicals they were exposed to in utero and see if that exposure could have long term effects,” explains Mandy Fisher, Senior Epidemiologist at Health Canada. “We started with kids at 6 months, and then between 2-5 years old, and now puberty. I think it’s fascinating what we have been able to learn by following these subjects.”

“While this study focuses solely on pregnant women and their children, it gives us a window into the impact of what happens in the womb,” adds Dr. Robin Shutt, Senior Study Coordinator at Health Canada. “Pregnancy is a really unique time, because normal functions protecting the body change substantially.”

Working with academic and clinical research partners nationwide, researchers started by studying pregnant women early in their pregnancy. Women were recruited from ten cities across Canada, completed a questionnaire and provided samples of their blood and urine several times, throughout pregnancy, after delivery.

With this information, researchers were then able to study the health of newborns and young children through to adolescence.

Specifically, the MIREC study measured metals and chemicals such as lead, mercury, phthalates and bisphenol A (BPA) in the mothers’ hair, milk, urine and blood.

Researchers also measured the same chemicals in baby’s first stool and its umbilical cord blood after birth.

 

MIREC Research Platform

MIREC Research Platform

The image presents the key phases of the MIREC research platform. The main elements of the project are:

  • MIREC (2008-2012) – Maternal health and creation of the biobank: Pregnancy and birth
  • MIREC-ID (2009-2012) – Birth outcomes, infant’s development and endocrine sensitive endpoints: Birth to 6 months
  • MIREC-CD plus (2013-2015) – Child’s growth and neurodevelopment: 2 to 5 years old
  • MIREC-ENDO phase 1 (2018-2021) – Puberty and metabolic markers for mom and child: 7-9 years old
  • MIREC-ENDO phase 2 (2022-2024) – Puberty, stress and metabolic markers for child: 10-12 years old
  • MIREC-ENDO phase 3 (2024-2027) – 13 to 15 years old

Throughout these phases, the Biobank collects and provides research data and biological specimens.

 

Since its beginning, MIREC has grown to have one of the most comprehensive datasets on prenatal exposure to environmental chemicals in the world, so far following almost 2,000 women and their children from 10 Canadian cities for over 10 years.

“There are short-term goals,” says Fisher. “But MIREC also has a long-term goal. If we can keep following this cohort, we can look at the long-term impacts on the children’s health, like fertility, and age at menopause in the moms as it relates to chemical exposure earlier in their lives. There are so many possibilities, if we can keep the cohort going!”

MIREC researchers are now collecting information from these children over time as they become teenagers. This type of cohort study is ideal to examine trends over time and see if there are any changes happening in a specific generation.

What they found

Through the data gathered from MIREC participants, researchers have published over 80 scientific articles in peer-reviewed journals detailing their findings.

These include information on exposure to chemicals such as lead and arsenic, with more to come. Over 100 researchers and trainees continue to analyze data gathered through various research projects.

Throughout the study, researchers collected and stored samples (including blood and urine) in a biobank freezer. Samples collected over several years may be used for future research on the health of mothers and their children, as funding becomes available.

For example, there are plans to look at the impact of cannabis on child neurodevelopment.

“There are so many pieces to the puzzle, and MIREC can provide one piece of the picture,” says Dr. Jillian Ashley-Martin, Research Scientist and Co-Principal Investigator of MIREC. “The project is giving us remarkable insights about the risk of these chemical exposures.”

“In our research, we’ve so far identified associations between exposure to chemicals and their health impacts. We aren’t yet able to identify the cause of the health effect observed,” explains Dr. Arbuckle. “To determine the cause would require several studies in different populations to have the same results. We aren’t there yet, but MIREC has provided us with a solid foundation from which we can continue to build.”

Next steps

Following the initial study, the team developed several follow-up studies that now form part of the MIREC research platform. Researchers are still in contact with over 1,400 mothers and their children. They are continuing to study child participants as they grow into adolescence, looking at the impact of exposure to chemicals on the onset of puberty.

The study is currently scheduled to conclude in 2028. “One of the questions that often comes up for us is why do we need to keep studying pregnancy? Aren’t we done now? I don’t think we are,” says Dr. Ashley-Martin. “We need to keep studying pregnant people because we are still learning how it’s a vulnerable time. We are studying people through their lives.”

In the future, researchers also hope to study the effect of chemicals on menopause. “I would like to study menopause in more details in MIREC moms,” says Dr. Maria Velez, Associate Professor in the Department of Obstetrics and Gynecology at Queen’s University and Principal Investigator for MIREC’s Kingston, Ontario site. “I want to measure the levels of AMH (a hormone produced in the ovaries that can tell us about the ovarian reserve) and see the change over the years. If we can compare the difference between previous levels and now, we can compare based on exposure to certain chemicals.”


The MIREC research is a key part of the Chemicals Management Plan. This plan seeks to reduce the risks posed by chemicals to Canadians and their environment by assessing chemicals used in Canada and by taking action on chemicals found to be harmful to human health and/or the environment.

Research like this provides information to decision-makers and can help guide their actions to change the future.

Stay tuned over the next few weeks for more articles about the MIREC studies throughout the different life stages of mothers and their children.

Up next: What every mother should know about environmental chemical exposure during pregnancy.

Find out more:

Maternal-Infant Research on Environmental Chemicals (MIREC) Research Platform

MIREC Canada