Reorienting Research: The Need to Bridge a Gap between Numbers and Context

After hearing about public health from an older friend attending university, she applied to and began her studies in the Department of International Health at Johns Hopkins University. There, she met many inspiring colleagues and friends who traveled the world studying the epidemiology of disease, an educational pathway that has led her to conduct research in communities around the world.

Dr. Kordas studies the intersection of food, nutrition and metal exposures in children. This research began quite narrowly – identifying if nutritional supplements could reduce lead levels and the cognitive/behavioral consequences of lead exposure among children in Mexico. She later launched similar research with children and their mothers at her research site in Montevideo, Uruguay. Over the years, due to research location and the evolution of research questions, she and her team expanded their research to understand the impact of metal mixtures, or co-exposures.

Environmental exposure to certain metals negatively affects cognitive abilities for school-going children – compromising their executive functioning, or the ability to plan and problem-solve, and to inhibit behavioral response. Therefore, much research has rightly focused on high-exposure levels on the one hand and on the other, the threshold of effects – a point at which metals are no longer causing harm. These findings help to inform public health professionals to design programs that reduce metal exposure in communities.

In many cases, a threshold of effect does not exist. This has led researchers like Dr. Kordas to begin asking questions about low-level exposures and low-level mixtures – if metal exposure levels are low, does that harm child health or development in any way? According to her research, depending on the mixtures, some metals appear to play more prominent roles than others. For example, one of Dr. Kordas’ students is looking at lead, arsenic, and cadmium and achieved height in 7-year old children. He found that lead was associated with lower height whereas other metals were not. Another paper under review looked at the same three metals and oxidative stress markers in these children, and a different metal has come to the forefront. These findings suggest that beyond thinking of “mixtures” as entities that behave in uniform ways, researchers need to pay attention to a variety of exposures (chemical and non-chemical) that underlie the outcomes they study.

A new concept in environmental health, the “exposome”, seeks to understand the totality of all chemical and non-chemical (stress, diet, physical activity, etc.) exposures humans’ experience. This concept is so new that researchers are still coming up with ways to measure and, importantly, integrate exposures. Traditional measurement methods detect the exposure to and the effects of metals from biomarkers in blood, hair, or urine. These methods can be accurate but arguably internalized and reduced. Biomarkers lack perspective of the broader social factors that lead to over-exposure such as forces that shape the process to ingestion, the types of dwellings in which children live, and the policies that increase likelihood of exposure. As such, researchers  are left with more questions than answers (e.g. even when one isolates all chemical exposures how does one operationalize a mixture, select a specific set for study, and equate a health outcome to that set of chemicals or other environmental factors?).

The exposome has the potential to reorient research methodologies to account for all potential exposure scenarios – from biology to geography to policy. Dr. Kordas and her team intend to contribute to this exciting and challenging field, however, she is confident that without a marriage between metrics and social science/public health thinking, we may understand how exposures affect human health but we will not be able to do anything about it.