The need to study multiple chemical exposures, not one at a time

Worldwide, communities near industrial operations, major highways, freight terminals and ports are highly exposed to multiple sources of chemical pollution. Historically, scientists have investigated hazardous exposures using a single-chemical approach that does not capture the health impact of cumulative exposures. Communities, health researchers, and the National Academies of Science are calling on scientists to use cumulative environmental frameworks to promote health.

To advance these new research approaches, PRHE and partners organized a symposium for the International Society for Exposure Science ISES2020 conference in September that explored the problems of single-chemical approaches and implications for health equity, environmental justice, and why community-engaged research is so important to address cumulative environmental stressors.

Symposium participant Dr. Kim Rhoads of UCSF Helen Diller Family Comprehensive Cancer Center shared how she partnered with San Francisco Bayview Hunter’s Point residents to conduct research and develop community-driven solutions to address the hazardous exposures and health inequities faced by residents. Dr. Rhoads stresses that “While the community intuitively senses the intersection between toxic exposures and health, intervention requires scientific evidence, an organized local body politic, and political will.”

Alongside Dr. Rhoads, J. Michelle Pierce, Executive Director of Bayview Hunters Point Community Advocates, described the community’s activism efforts, experiences and frustrations. She emphasizes that “Single chemical approaches to exposure assessment discount the lived experience of residents, especially for communities of color.”

The Bayview Hunters Point community, located in southeast San Francisco, has spent decades advocating for health-protective policies around toxic pollutants and the need for cumulative environmental exposure frameworks to achieve social justice. Since World War II, Bayview Hunters Point naval shipyard, that includes the historical site of the US Navy Radiological Defense Laboratory (NRDL), has been one of the country’s most contaminated Superfund sites. The NRDL left behind known environmental contaminants, including industrial chemicals, air pollutants, heavy metals and other known carcinogens.

Racist practices of redlining neighborhoods and allowing hazardous land uses next to residential areas, have significantly contributed to high rates of poverty, social deprivation, chronic disease, and poor health outcomes in the surrounding community. Bayview Hunters Point residents have suffered from higher rates of asthma (with the highest rate of asthma hospitalizations in San Francisco in 2000), breast cancer (Bayview resident African American women aged <50 years had twice the rate of breast cancer compared to San Francisco as a whole in mid 1990s), cervical cancer, and prostate cancer.

Scientific studies and regulatory practices that focus on isolating a single chemical to study or to regulate, do not serve communities such as Bayview Hunters Point that are exposed to multiple environmental chemicals as well as other non-chemical stressors.

Single-chemical approaches not only fail communities but also fail to meet rigorous scientific standards that fully evaluate risk. To demonstrate the failings of this approach, PRHE Director Tracey Woodruff reviewed the latest phthalates exposure research. Phthalates are a class of chemicals found in virtually all of the U.S. population and are known to put healthy pregnancies and fetal development at risk. In 2001, the US Centers for Disease Control published the National Report on Human Exposure to Environmental Chemicals, a study using biomonitoring data for 27 chemicals in the U.S. population from 1999 NHANES data, that included phthalates. The biomonitoring program documented in the report expanded the number of chemicals monitored within a representative sample of US residents. Eventually, exposure documented in biomonitoring, and consumer and environmental advocacy led to the ban of one type of phthalate, but other types of phthalates were substituted, and subsequent biomonitoring showed marked increases in the substitutes. Regrettably, substitutes can also put the population at risk, illustrating how not focusing on a class of chemicals could underestimate the health impacts and lead to ongoing exposures.

We join with communities and health researchers to call on regulatory agencies and exposure scientists to rapidly advance their science to systematically employ cumulative environmental frameworks to promote health.