The Human Health Risk Study Report-Back: The Malden River is Cleared for Public Boating

For nearly 150 years, the Malden River in Massachusetts served as an industrial waste dumping site for oil refineries, coal processing plants, tanneries, and chemical factories.  Despite this history of heavy contamination, no reliable information existed about the health risks of recreating on the river.  This situation was recently remedied.  A research study has just been completed by Gradient Corporation, MIT CEHS and the Mystic River Watershed Association to provide an independent and comprehensive human health risk assessment for the river.  The news was excellent; the results showed that health risks for cancer are negligible for recreational boating on the Malden River.

Report-Back Provided to the City of Malden

Dr. Kathleen Vandiver, MIT’s CEHS Community Outreach Education and Engagement Core (COE2C) Director, presented the results of the human health risk study to the Malden City Council on May 23, 2019 after meeting earlier in the month with Malden Mayor, Gary Christenson.  The City Councilors meeting was live streamed by MaldenAccessTV and published on April 24, 2019.


“In the absence of a rigorous health risk analysis, ‘stay away from the water’ has been the logical and appropriate precautionary advice given to the public in prior years. This report now represents a breakthrough for the recreational use of the river,” said Dr. Vandiver of the Massachusetts Institute of Technology’s Center for Environmental Health Sciences (MIT CEHS) and a member of the Friends of the Malden River (FoMR).

Overview of the work

For the purposes of this study, sediment samples from the Malden River were collected during the summer of 2017 by the Mystic River Watershed Association and analyzed for contaminants in certified laboratories, funded by MIT CEHS.  The sediment samples were collected from nine locations (See the Malden River Map), seven from potential public boat launch locations and two from existing boathouse launches. These were the Malden High School and Tufts University sites, indicated on the map as (1) MRC and (2) RE Dock respectively.  Water samples were also collected from multiple locations along the river.

Health Risk Methods

With the concentrations of contaminants at these locations in hand, analysts calculated the health risks faced by boaters who might come in contact with the water and sediments. To do this, the analysts considered a wide range of boaters, children, casual paddlers, and frequent competitive boaters.

Importantly, they assumed that all boaters would frequently be exposed to maximal amounts of sediments and water. For example, the analysts assumed that boaters would capsize every time they went out; they would wade through sediments up to their knees every time they launched; and they would swallow water and sediments on every trip as well. This kind of risk study is called a “conservative” study, because it incorporates maximal risk factors into the calculations, thus generating a wide margin of safety. 

Results favorable for boating    

No result from the Malden River risk study exceeded U.S. EPA's limit of 1 cancer case per 10,000 individuals.  Additionally, no Malden River result exceeded the Massachusetts Department of Environmental Protection Agency’s tougher limit set at 1 cancer case per 100,000 individuals.  Thus all risks for boaters on the Malden River are within acceptable environmental health risk levels set by the both the state and federal governments.

Furthermore, boaters will probably not ever experience the worst-case risk levels produced in the study because they will not be capsizing on every outing.  Also boaters on the Malden launch from the docks along the river -not by wading through the sediments.    

“With this important information in hand-we now must turn to expanding access to the river through parks, paths and boat launches-priorities outlined in our community-driven Malden River Vision Plan,” said Patrick Herron, Executive Director of the Mystic River Watershed Association (MyRWA). “The great news is that there are awesome municipal and community partners that are committed to making a difference.”

Project Funders & Partners

This study was funded in part by the Lewellyn Foundation, the Fine Foundation, Preotle Lane & Associates, Mystic River Watershed Environmental Fund, and Mystic Valley Development Corp. The Mystic River Watershed Association, MIT CEHS, and Gradient Corp. provided in-kind support.

"The Human Health Risk Study on the Malden River is a prime example of an important collaboration initiated with an idea from our community,” said Karen Buck, Friends of the Malden River. “Since 2016, together with MyRWA, we formed partnerships that overcame the funding shortage.  This collaboration created a meticulous, independent, and unarguable study providing the community with assurance that yes, it is safe to boat on the Malden River.  The sense of relief and joy is palpable. Now the work begins!“

This CEHS article was adapted from a prior article written for the Mystic River Watershed Association; posted 10 April, 2019.