USGS News

USGS Continues to Write History

Summary: The fourth volume of the comprehensive history of the U.S. Geological Survey, Minerals, Lands, and Geology for the Common Defence and General Welfare: Volume 4, 1939‒1961, has been issued as an electronic document. New Volume of Agency Annals Released

Contact Information:

Jon Campbell ( Phone: 703-648-4180 );



The fourth volume of the comprehensive history of the U.S. Geological Survey, Minerals, Lands, and Geology for the Common Defence and General Welfare: Volume 4, 1939‒1961, has been issued as an electronic document.

Featuring more than 200 illustrations, the 704-page Volume 4 focuses on the United States and the USGS in war and peace from the beginning of World War II in Europe to the end of the administration of President Dwight D. Eisenhower. During this period, the USGS developed and adapted new instruments and methods that included airborne magnetometers and radiometers, advanced seismometers, stereoscopic plotters for topographic mapping, geophysical logging (detailed records of geologic formations penetrated by a borehole), and geological sampling from deep wells. 

The late Mary C. Rabbitt (1915‒2002), a geophysicist who served with the USGS (1949‒1978), wrote the first three volumes in the series: Volume 1, Before 1879 (1979), Volume 2, 1879‒1904 (1980), and Volume 3, 1904‒1939 (1986). Volume 4 was begun by Rabbitt and completed by coauthor Clifford M. Nelson, a geologist with the USGS since 1976. 

Like the earlier books in the series, Volume 4 places USGS operations in mapping and the earth sciences within the wider contexts of national and international history. For instance, USGS development of the airborne magnetometer — an instrument that traces the Earth’s magnetic field, enabling an effective method of exploring for subsurface minerals — followed from a wartime device that U.S. forces used to hunt enemy submarines in World War II. 

In the foreword to Volume 4, Mark D. Myers, the 14th USGS Director (2006‒2009), wrote that the volume records USGS support of the Nation’s efforts during "a pivotal interval of transformation for the United States and the agency, …a time of great national sacrifice, rapid expansion of industrial capacity, spectacular scientific and technological advancement, and international leadership." 

Projected Warming of Wisconsin Streams Could Negatively Affect Trout

Summary: Annual average stream temperatures in the Trout Lake watershed, Wisconsin, could increase from one to three degrees Celsius by the year 2100, which might negatively affect cold water fish like brook trout

Contact Information:

Marisa Lubeck ( Phone: 303-202-4765 );



Annual average stream temperatures in the Trout Lake watershed, Wisconsin, could increase from one to three degrees Celsius by the year 2100, which might negatively affect cold water fish like brook trout.  

The U.S. Geological Survey recently modeled the effects of climate change on stream temperatures for three recreational fishing creeks near Eagle River, Wisconsin, from years 2000-2100: Stevenson Creek, North Creek and Upper Allequash Creek. Findings suggest that daily mean stream temperatures in Stevenson Creek, the warmest of the three streams, could become too high to sustain a healthy trout population by the turn of the century. 

“A persistent increase in daily mean stream temperature can affect the diversity of fish species in northern Wisconsin,” said USGS scientist William Selbig. “This study can be used by managers to help make important conservation decisions in the Trout Lake watershed.” 

The new USGS report, authored by Selbig, is published in the journal Science of the Total Environment

Summer stream temperature is the most important single factor influencing distribution and production of some cold water fishes. Streams that may currently be suitable as a cold water sport fishery, like those in the new study, could become increasingly fragmented as fish seek refuge from warming water temperatures to less impacted areas. 

Brook trout populations are most stable when temperatures do not exceed 19 degrees Celsius, or about 66 degrees Fahrenheit. Selbig found that the frequency at which daily mean stream temperatures exceeded ideal ranges for brook trout increased for Stevenson Creek and North Creek during the last five years of the study period, especially in the warm summer months of July and August. 

“Some emission scenarios indicate that Stevenson Creek could become too warm to maintain its status as a Class II trout stream,” Selbig said.  

However, the coolest of the three streams, Upper Allequash Creek, appeared resilient to climate warming, with temperatures remaining suitable for cold water fish the majority of time. 

The projections showed that by 2100, annual average temperatures could increase by:

  • 1.7 to 3.2 degrees Celsius in Stevenson Creek,
  • 1.4 to 2.9 degrees Celsius in North Creek and
  • 1.1 to 2.2 degrees Celsius in Upper Allequash Creek. 

For more information on water resources in Wisconsin, please visit the USGS Wisconsin Water Science Center website

Model Offers More Ease, Precision for Managing Invasive Asian Carp

Summary: The likelihood of Asian carp eggs being kept in suspension and hatching in the St. Joseph River in Michigan has been further evaluated using a model that examines a range of multiple flow and water temperature scenarios

Contact Information:

Jennifer LaVista ( Phone: 303-202-4764 ); Elizabeth Murphy ( Phone: 217-328-9726 );



The likelihood of Asian carp eggs being kept in suspension and hatching in the St. Joseph River in Michigan has been further evaluated using a model that examines a range of multiple flow and water temperature scenarios. Results illustrate the highest percentage of Asian carp eggs at risk of hatching occurs when the streamflow is low and when the water temperature is high. This new study by the University of Illinois and the U.S. Geological Survey is published in the Journal of Great Lakes Research.

“In this study, the Fluvial Egg Drift Simulator (FluEgg) model allowed us to examine the complex dependencies between flow, temperature and egg development,” said USGS hydrologist Ryan Jackson. “This information provides resource managers with a range of conditions under which the St. Joseph River is vulnerable to Asian carp reproduction."

The FluEgg model was used to evaluate egg movement and the likelihood of successful Asian carp reproduction under different streamflow and temperature conditions representative of historical spawning seasons in the St. Joseph River, a tributary to Lake Michigan. Results show that eggs develop faster at warmer water temperatures, therefore requiring less time to drift in the river until hatching. Low streamflows can also be conducive to reproduction when the streamflow is just fast enough to keep most of the eggs in suspension while allowing for the greatest amount of drift time before reaching the lake, thus increasing the likelihood of hatching.

The FluEgg model, developed by University of Illinois researchers in collaboration with the USGS, was first introduced in 2013. The latest version of the model is available online, and includes a user-friendly interface and improved predictions of egg transport in rivers.

Invasive Asian carp consume plankton from the base of the food web and reproduce prolifically which could pose substantial environmental risks and economic impacts to the Great Lakes if they become established. 

"This work focuses on the early life stages of Asian carp," said USGS research fish biologist Duane Chapman. "Targeting early life stages can include disrupting spawning activities or egg development in rivers where Asian carp spawn."

Several factors affect the viability of the eggs. The temperature of the water affects how long the eggs need to hatch, and the velocity of the river affects the movement of the eggs and whether the eggs remain in suspension or sink to the bottom. Eggs that settle on the riverbed will likely die, and eggs that are transported down the river and into a lake may not have enough time to develop to the hatching stage before settling to the lakebed.

The reproduction assessment of Asian carp eggs in the St. Joseph River demonstrated the complexity of the problem where the length of the river, velocity and water temperatures cannot be assessed individually. Rather, a holistic analysis is required, where egg development, water-quality characteristics and the hydrodynamics of the river are interconnected and analyzed together. 

“Successful reproduction requires a fine balance between the rate of egg development and the variable flow conditions present in a river required to maintain the eggs in suspension,” said Tatiana Garcia, USGS research hydrologist and lead author of the paper.

The paper, “Application of the FluEgg model to predict transport of Asian carp eggs in the St. Joseph River (Great Lakes tributary)” by Tatiana Garcia, Elizabeth A. Murphy, Patrick R. Jackson and Marcelo H. Garcia, is available online. 

Many Dry Tortugas Loggerheads Actually Bahamas Residents

Summary: Many loggerhead sea turtles that nest in Dry Tortugas National Park head to rich feeding sites in the Bahamas after nesting, a discovery that may help those working to protect this threatened species New Information May Help Protect Threatened Turtle

Contact Information:

Kristen Hart ( Phone: 954-236-1067 ); Gabrielle Bodin ( Phone: 337-266-8655 );



GAINESVILLE, Fla.—Many loggerhead sea turtles that nest in Dry Tortugas National Park head to rich feeding sites in the Bahamas after nesting, a discovery that may help those working to protect this threatened species. 

Researchers from the U.S. Geological Survey used satellites to track the population of loggerheads that nest in the Dry Tortugas – the smallest subpopulation of loggerheads in the northwest Atlantic – and found the turtles actually spend a considerable portion of their lives in the Bahamas, returning to the Dry Tortugas to nest every two-to-five years. They then spend three-to-four months nesting in the Dry Tortugas before returning to the Bahamas.

This new information will help resource managers better identify areas to target for conservation efforts.

“Collaborative conservation efforts focused on protecting important loggerhead residence and foraging areas between the United States and Bahamas could offer significant protection for the Dry Tortugas loggerheads,” said USGS Research Ecologist Kristen Hart, lead author of the study. “Two other subpopulations of loggerheads that nest in Northern and Peninsular Florida and also travel to residence areas in the Bahamas would benefit from this protection as well.”

The current estimate of the subpopulation of loggerheads that nest in the Dry Tortugas hovers between 258–496 females. Populations of the turtle are difficult to estimate. Loggerheads start nesting when they are approximately 25 years old, and then nest every two-to-five years until they die. Researchers have found that marking females that return to the same beach to nest every two-to-five years is the most practical way to get an indication of population size.

The northwest Atlantic population of loggerhead turtles is listed as “threatened” under the Endangered Species Act, which provides them protection from intentional harm or harvest and protects their most important habitats within the United States and its waters.

In this study, researchers tracked marked turtles over six nesting seasons. Results showed the turtles selected almost the exact same residence area in the Bahamas during their second tracking event. In addition, tracking data showed that individual residence areas generally did not overlap, leading the scientists to believe that loggerheads at this foraging ground may establish territories.

Turtles tagged in more than one Dry Tortugas nesting season showed similar migration paths and timing as compared to their own previous migrations. Their migratory paths included the Florida Strait, a major shipping fairway where ship strikes could threaten the turtles.

After traveling through non-protected waters from the Dry Tortugas, the turtles primarily selected residence areas in non-protected zones once reaching the Bahamas. Although direct turtle harvest has been illegal in the Bahamas since 2009, commercial fishing has the potential to impact the loggerheads’ food resources and poses a direct threat to them as they can become entangled in lines attached to gear.

Loggerhead sea turtles are primarily carnivorous and feed mostly on shellfish that live on the bottom of the ocean, such as horseshoe crabs, clams, mussels, and other invertebrates. Their powerful jaw muscles help them to easily crush the shellfish. Once reaching sexual maturity, the turtles nest every two-to-five years, depositing two-to-six clutches of 75 to 120 eggs approximately every two weeks during the nesting season. After nesting, they migrate back to their foraging site.

The Northwest Atlantic loggerhead nesting numbers declined sharply in the 1990s followed by an increase over the last six years making it difficult to assess the trend at this point. Scientists remain concerned about the ongoing threats to this population which include loss or degradation of nesting habitat from coastal development and beach armoring; disorientation of hatchlings by beachfront lighting; nest predation by native and non-native predators; degradation of foraging habitat; marine pollution and debris; watercraft strikes; disease; and incidental take from channel dredging and commercial trawling, longline and gill net fisheries. 

Future studies to characterize the resources within residence areas and individual loggerhead behaviors at their residence areas will also help to guide conservation efforts.

The study, “Bahamas connection: residence areas selected by breeding female loggerheads tagged in Dry Tortugas National Park, USA,” by Kristen M. Hart, USGS; Autumn R. Sartain, a contractor with the USGS; and Ikuko Fujisaki, University of Florida, is available online.

Genetics Provides New Clues about Lionfish Invasion

Summary: New genetic data suggest the red lionfish invasion in the Caribbean Basin and Western Atlantic started in multiple locations, not just one as previously believed, according to a new study led by the U.S. Geological Survey

Contact Information:

Margaret Hunter ( Phone: 352-264-3484 ); Christian Quintero ( Phone: 813-352-3487 );



GAINESVILLE, Fla.— New genetic data suggest the red lionfish invasion in the Caribbean Basin and Western Atlantic started in multiple locations, not just one as previously believed, according to a new study led by the U.S. Geological Survey.

Florida has often been cited as the likely location of the introduction, but the new research suggests multiple introductions occurred, with some potentially coming from the more southern parts of the range. The Caribbean Basin stretches from parts of Florida’s Gulf Coast through South America.

Genetically unraveling the progression of the red lionfish invasion and determining if introductions are still occurring could help guide response and control efforts for this and other invasive fishes. The spiny fish is well known as a predatory invasive species that negatively impacts its non-native environment, disrupting marine food webs as they prey in coral reef ecosystems on invertebrates and fish, including game fish juveniles, such as snappers and groupers. Lionfish are native to the Indo-Pacific region, and were likely brought to the United States via the pet trade.  

USGS researchers analyzed red lionfish samples from fourteen countries and territories in the Greater Caribbean and Western Atlantic in an effort to better understand the invasive species’ population structure and dispersal patterns. While red lionfish can be found in the Gulf, this study did not include any samples from that region. 

 “The red lionfish can be used to help up understand other non-native populations and their invasion dynamics,” said USGS geneticist Margaret Hunter. “The more we know about this species and its progression, the more we can help resource managers and others fighting the invasion be prepared to help control lionfish colonization in new locations. Ultimately, any information gleaned from this species could be applied to managing and assisting with eliminating future invasive species.”

Researchers found that unique regional genetic patterns separated the studied area into northern and southern regions, with the split occurring near the Bahamas. Given the regional genetic differences revealed in this study, the researchers now suspect multiple introductions. One rare genetic strain was found in only a few samples in the southern region, but was pervasive in the north.

“Studying the genetic strains across regions gives us insight into how these fish are spreading. Dispersal against the flow of ocean currents may explain why we see this rare strain in the south, but even if that is the case, additional support for multiple introductions exists; the genetic patterns found in this study support the idea of multiple introductions, and could be due to additional releases in the south,” said John Butterfield, a USGS contract biologist and lead author of the publication.

Continued releases would increase the potential for more genetically diverse red lionfish to join the current population, which could counter future removal efforts or allow them to more rapidly expand their range beyond current boundaries.

The broad dispersal of red lionfish may in part be due to their reproductive habits. Females can spawn up to once every four days, which could result in one female releasing up to two million eggs a year. Following spawning, larvae can disperse long distances via ocean currents, for up to 35 days.

In the United States, federal and state agencies are working together to help combat this invasive fish through the Aquatic Nuisance Species Task Force. This intergovernmental entity has drafted a National Invasive Lionfish Prevention and Management Plan that is in the final stages of approval. The main goals of the plan are to prevent the spread of invasive lionfish; coordinate early detection and rapid response efforts; control and management of the current invasive population; and fully assess the impact that the invasion is having on native species and habitats.

The full study is available online. More information on USGS Southeast Ecological Science Center’s genetics work is available at its genetics website, or on its genetic research fact sheet.

Do You Like to Map? Take the Mapping Challenge!

Summary: Volunteer citizen-mappers continue to make significant contributions to the USGS ability to provide accurate mapping information to the public The USGS crowd-sourcing project volunteers have updated all law enforcement points in Tennessee

Contact Information:

Elizabeth McCartney ( Phone: 573-308-3696 ); Mark Newell ( Phone: 573-308-3850 ); Erin Korris ( Phone: 303-202-4503 );



Volunteer citizen-mappers continue to make significant contributions to the USGS ability to provide accurate mapping information to the public. Recently, volunteers were asked to update all of the law enforcement structure points in Tennessee. The volunteers answered the call and added, verified, edited, or deleted an amazing 440 points!

In addition, all of the points were quality checked by either a peer reviewer or an advanced editor, so the data was ready to go into The National Map at the conclusion of the challenge.

The volunteer additions and edits will be symbolized on US Topo maps during the next production cycle for Tennessee, slated for next year.

An exciting addition to the mapping project is Mapping Challenges. The Challenges asks volunteers to concentrate on specific areas and structure types that need updating. In addition, Challenges encourage volunteers to remain engaged, and incentivizes participation. Once a need is determined, a call to action goes out to the volunteer corps with information on the geographic location and the type of structures that needs updating. Volunteers who participate can earn a series of virtual recognition badges and are recognized on social media and TNMCorps project site.

Using crowd-sourcing techniques, the USGS Volunteered Geographic Information (VGI) project, known as The National Map Corps (TNMCorps), encourages volunteers to collect manmade structures data in an effort to provide accurate and authoritative spatial map data for the National Geospatial Program’s web-based The National Map. Structures being updated include schools, hospitals, post offices, police stations and other important public buildings.  

Special thanks to the volunteers who participated in this challenge: fconley, HGeisler, Cartograsaurus, TheJ, BCook2, rjerrard, Vindalou, Jwo_rocks, wesward, and alherna4.

"At times, locating structures seems similar to solving puzzles or detective work,” commented fconely, a Challenge veteran and one of the project’s more active participants.

Tools on TNMCorps project site explain how a volunteer can edit any area, regardless of their familiarity with the selected structures, and becoming a volunteer for TNMCorps is easy; register by going to The National Map Corps Editor. If you have access to the Internet and are willing to dedicate some time to editing map data, we hope you will consider participating.

Screen-shot of the Tennessee Law Enforcement Facility Mapping Challenge showing the more than 440 edited points (green dots). At this scale, many dots contain more than one edited or verified structure. (high resolution image) The most recent status graphic showing the number and density of The National Map Corp submitted edits or verification for the past three years. (high resolution image)

USGS & Clear Channel Outdoor Launch Earthquake Preparedness Campaign Reminding Californians To Prepare For Inevitable Earthquakes

Summary: The U.S. Geological Survey and Clear Channel Outdoor today announced a partnership to provide the public with critical earthquake safety information during April Clear Channel Outdoor Donates Outdoor Advertising Space to Federal Earth Science Agency Providing Public with Critical Safety Information

Contact Information:

Dagny Akeyson ( Phone: 818-760-2121 ); Donyelle  Davis ( Phone: 626-202-2393 );



Los Angeles, Calif. – The U.S. Geological Survey and Clear Channel Outdoor today announced a partnership to provide the public with critical earthquake safety information during April. In support of the campaign, CCO is donating space on digital billboards throughout the Southland to help spread this important message and encourage Californians to prepare before it’s too late.

The billboards direct SoCal residents to visit the Earthquake Country Alliance’s website at EarthquakeCountry.org, where they can learn techniques for preparing before an earthquake, surviving during one, and recovering after a tremor. The USGS is an active leader in the ECA, which is a statewide public-private partnership of people, organizations, and regional alliances that work together to improve preparedness, mitigation and resiliency. The advertisements will run through the month of April.

“Almost everyone could make their family, home or business safer through retrofitting their buildings, securing their space or other proactive steps to prepare themselves, their families, and their homes for the next earthquakes,” said Lucy Jones, Science Advisor for Risk Reduction at USGS. “We’re pleased to join Clear Channel Outdoor in spreading this important public safety message to residents throughout Southern California. By placing these messages on digital billboards region-wide we can be sure that communication reaches residents and reminds them that ‘we are all in this together,’ and we each need to do our part to protect our whole community." 

Southern California has the highest earthquake risk of any region in the United States. Not only is the area bisected by the San Andreas Fault, which is capable of producing very large quakes, but is also crisscrossed by many other faults capable of producing large and damaging tremors. While many have been warned of the “big one,” quakes of lesser magnitude, including the 1994 Northridge Earthquake, can and have caused significant damage, making it imperative that residents are proactively prepared for the potentially devastating aftermath of an emergency earthquake situation.

“We live in a high-risk region, yet we often forget that the next big earthquake could be right around the corner. During this year’s Earthquake Preparedness Month, we are urging citizens to take action and prepare by planning ahead and arming themselves with knowledge,” said Los Angeles City Councilmember Mitchell Englander, who represents the Northridge community. “I’m pleased to see the USGS and Clear Channel Outdoor bringing this important message to Angelenos and encourage citizens who see the message to take proactive steps to protect themselves.”

The USGS and CCO-led campaign encourages the public to seek additional information about earthquake safety to ensure they are prepared for tremors in the quake-prone Southern California region. This earthquake preparedness campaign is not the first time CCO has partnered with organizations to help drive awareness about the importance of earthquake preparedness, as CCO previously participated in similar earthquake preparedness campaigns surrounding the anniversary of the Northridge Earthquake.

“Southern California is a hotbed for quakes, making it ever more critical that residents take proactive steps to prepare for emergency earthquake situations,” said Layne Lawson, director of public affairs for Clear Channel Outdoor. “Clear Channel Outdoor is proud to join USGS in the effort to communicate this critical message to the Southland community and assist with this important public safety effort. We are pleased that our digital billboards will play a role in the emergency preparedness of the region and are glad to lend our resources to urge Californians to properly safeguard their families and homes.”

The unique ability of digital signs to reach a wide audience while displaying messages in real-time allows them to act as valuable resources in the fight against crimes, like human trafficking, that occur around us every day. CCO has routinely lent these tools to support real time, life-saving messaging like AMBER Alerts, FBI and U.S. Marshall Wanted notices and emergency notifications.  The boards are also a useful tool for non-profit organizations, public safety agencies, law enforcement and a variety of others who need to effectively relay messages to the public. 

Some Coastal Communities May Not Have Time for Tsunami Evacuation

Summary: Tens of thousands of people along the U.S. Pacific Northwest coastline may not have enough time to evacuate low-lying areas before tsunami waves arrive, according to a new publication by researchers at the U.S. Geological Survey, University of Colorado Boulder, and California State University, Sacramento

Contact Information:

Leslie  Gordon ( Phone: 650-329-4006
 );



The city of Nehalem, Washington, shown with the internationally-adopted tsunami-evacuation sign. (High resolution image)

PORTLAND, Ore. — Tens of thousands of people along the U.S. Pacific Northwest coastline may not have enough time to evacuate low-lying areas before tsunami waves arrive, according to a new publication by researchers at the U.S. Geological Survey, University of Colorado Boulder, and California State University, Sacramento. 

“All coastal communities in the U.S. Pacific Northwest are vulnerable to varying degrees to tsunami hazards from a Cascadia subduction zone earthquake,” said Dr. Nathan Wood, lead author of the study and scientist with the USGS. “Having a better sense of how a community is specifically vulnerable provides officials with the ability to develop outreach, preparedness, and evacuation plans that are tailored to local conditions and needs.” 

The authors detail their findings in the scientific journal “Proceedings of the National Academy of Sciences.” They examined the 49 cities, seven tribal reservations, and 17 counties from northern California through northern Washington that are directly threatened by tsunami waves that could be generated by a future Cascadia subduction zone earthquake.  The scientists evaluated the number of people or businesses exposed to tsunami hazards, as well as demographics and evacuation time by foot for each of these communities.

In their analysis, scientists found that coastal communities fell into one of three groups differentiated by the size of their population and the time it would take to safely evacuate people. Communities in the first group have relatively small populations in tsunami hazard zones and likely have sufficient time to evacuate, suggesting the need for tsunami education. A second group of communities has large populations in tsunami-hazard zones and likely will have sufficient time to evacuate if people are able to move quickly, suggesting a need for evacuation training. The third group of communities has moderate-sized populations in tsunami hazard zones, but insufficient time for everyone to evacuate before wave arrival, suggesting the need for solutions such as vertical-evacuation refuges.

“This new research confirms the underlying need for continuing the important public education efforts to ensure coastal residents know how to reach safety in the event of a tsunami,” said John Schelling, Earthquake & Tsunami Program Manager for the Washington Military Department’s Emergency Management Division. “Perhaps more importantly, this research confirms the need for continued implementation of the multi-agency collaboration known as “Project Safe Haven” and ensuring communities on the Washington Coast have tsunami vertical evacuation refuges, from which to escape a tsunami.”

“Identifying communities with similar tsunami hazard vulnerabilities will build a regional network among officials to share success stories of risk reduction and create opportunities for collaboration,” said Wood. “Our goal was to provide officials with actionable information for saving lives with community-specific interventions.”

The full study, “Community clusters of tsunami vulnerability in the U.S. Pacific Northwest,” is available online from the journal publisher.

The USGS is leading studies of community vulnerability to various natural hazards through its Land Change Science Program. For further information on this study and other current projects across the United States, visit the USGS Risk and Vulnerability to Natural Hazards project.

Coal-Tar-Sealant Runoff Causes Toxicity and DNA Damage

Summary: Runoff from pavement with coal-tar-based sealant is toxic to aquatic life, damages DNA, and impairs DNA repair, according to two studies by the U.S. Geological Survey published in the journals Environmental Science and Technology and Science of the Total Environment

Contact Information:

Barbara Mahler ( Phone: 512-927-3566 ); Jennifer LaVista ( Phone: 303-202-4764 );



Runoff from pavement with coal-tar-based sealant is toxic to aquatic life, damages DNA, and impairs DNA repair, according to two studies by the U.S. Geological Survey published in the journals Environmental Science and Technology and Science of the Total Environment.

Pavement sealant is a black liquid sprayed or painted on the asphalt pavement of parking lots, driveways and playgrounds to improve appearance and protect the underlying asphalt. Pavement sealants that contain coal tar have extremely high levels of polycyclic aromatic hydrocarbons (PAHs).  Coal tar is a known human carcinogen; several PAHs are probable human carcinogens and some are toxic to fish and other aquatic life.

Rainwater runoff collected as long as three months after coal-tar-sealcoat application caused 100% mortality to minnows and water fleas, which are part of the base of the food chain, when the test organisms were exposed to ultra-violet radiation to simulate sunlight. The full study, reported in the scientific journal Environmental Science and Technology, is available online.

Exposure of fish cells to coal-tar sealant runoff damaged their DNA and impaired the ability of the cells to repair DNA damage. “The simultaneous occurrence of DNA damage and impairment of DNA repair has important implications for cell health,” said Sylvie Bony, who led the study at the Ecole Nationale des Travaux Publics de l’Etat (ENTPE), a French research agency in Lyon, France. The study is reported in the scientific journal Science of the Total Environment.

The studies were done to address the concern that rainfall runoff occurring within hours or days of coal-tar-based sealant application might be toxic to fish and other organisms in streams. The two studies collected and tested simulated runoff at various times beginning just hours after coal-tar-sealant application. 

"The USGS has been studying coal-tar-sealcoat as a source of PAHs for 10 years, and findings from these two studies are consistent with what is known about toxicity and genotoxicity of these chemicals," said USGS scientist Barbara Mahler.

A previous publication detailed the chemical concentrations in runoff from coal-tar-sealed pavement at a range of times following sealant application. The results, reported in the scientific journal Environmental Pollution, are available online.

Coal-tar sealants have significantly higher levels of PAHs and related compounds compared to asphalt-based pavement sealants and other urban sources, including vehicle emissions, used motor oil, and tire particles. Previous studies have concluded that coal-tar sealants are a major source of PAHs to lake sediments in commercial and residential settings, and that people living near pavement sealed with coal-tar sealant have an elevated risk of cancer.

To learn more, visit the USGS website on PAHs and sealcoat.