Person in waders standing in stream collecting water
A technician collects a water sample from a stream at Indiana Dunes National Lakeshore.

NPS photo

You may have heard the saying “all drains lead to the lake,” but it can be hard to remember that includes what is sent down sinks, toilets, and washing machines. Many things we do in the course of a day can contribute to the contamination of surface waters (lakes and streams) in ways we cannot see. Some of these “every day chemicals” are known as contaminants of emerging concern.

In 2013, the Great Lakes Network joined six other Inventory and Monitoring Networks and the U.S. Environmental Protection Agency (USEPA) in a study analyzing samples from park surface waters for wastewater indicators, pharmaceuticals, personal care products, and pesticides. From 2013 through 2015 we collected surface water samples from four parks—Apostle Islands National Lakeshore, Indiana Dunes National Lakeshore, Isle Royale National Park, and Mississippi National River and Recreation Area. Samples from Isle Royale were not analyzed for wastewater indicators.

Table1. Detection frequency and maximum concentration of detected wastewater indicators analyzed in a subset of samples in 2013 and 2014.
Chemical Chemical Class Detection Frequency (%) Maximum Concentration (ng/L)
Mississippi National River and Recreation Area (2013)
Bisphenol A Plastic component 50 232
Caffeine Stimulant 50 43.3
Galaxolide Synethetic fragrance 33 115
Metolachlor Herbicide 17 867
Tributyl phosphate Plasticizer/flame retardant 33 68.6
Triethyl citrate Plasticizer 17 146
Apostle Islands National Lakeshore (2014)
Bisphenol A Plastic component 12 56.2
Tri(dichloroisopropyl) phosphate Plasticizer/flame retardant 12 50.9
Triclosan Antimicrobial 12 74.9
Indiana Dunes National Lakeshore (2014)
Acetophenone Fragrance 40 67.7
Bisphenol A Plastic component 40 350
Caffeine Stimulant 20 215
Camphor Fragrance 20 89.6
Equilenin Estrogen 20 187
Estrone Estrogen 20 121
Methylsalicylate Fragrance 20 53.4
Triphenyl phosophate Plasticizer/flame retardant 20 82

Estrogen, medications, DEET, and more

More chemicals and higher concentrations were detected at the two urban parks (Mississippi River and Indiana Dunes) than at the two more remote parks (Apostle Islands and Isle Royale). Fourteen wastewater indicators were detected across the three parks analyzed, including two forms of estrogen (Table 1), both of which were detected in the same sample at concentrations >100 ng/L. Concentrations of >5 ng/L are known to affect the reproduction of at least one species of minnow.

At Indiana Dunes and Mississippi River, pain relievers, anticonvulsants, antidepressants, and diuretics were the most frequently detected pharmaceuticals (Table 2). Gabapentin, an anticonvulsant, had the highest concentration of all detected pharmaceuticals.

Bisphenol A, an industrial chemical used primarily to make polycarbonate plastic and epoxy resins, and organophosphate flame retardants were commonly detected wastewater indicators at all three sampled parks.

Simazine had the highest observed concentration among herbicides (>1000 ng/L) in two samples, both from Indiana Dunes. Those two, along with concentrations of metolachlor, another herbicide, at Mississippi River, were similar to concentrations reported for other major urban rivers in the United States. None of the samples exceeded the Maximum Contaminant Levels for herbicides in drinking water set by the USEPA.

With the exception of a few chemicals, detected concentrations were generally far below screening values or benchmarks at which human health can be affected. The exceptions were metformin, atrazine, and simazine, which each had concentrations approaching available human-health benchmarks in at least one sample, and hydrochlorothiazide (a diuretic medication), which exceeded a human health-based screening value in seven samples.

Table 2. Detection frequency and maximum concentration of pharmaceuticals, personal care products, and pesticides detected in at least 30% of samples collected at each national park.
Chemical Chemical Class Detection Frequency (%) Maximum Concentration (ng/L)
Mississippi National River and Recreation Area (2013-2014)
2,4-Dichlorophenoxyacetic acid Herbicide 100 172
Acetochlor Herbicide 50 265
Acetochlor oxanilic acid Herbicide by-product 95 896
Atenolol Medication (blood pressure) 35 30.5
Atrazine Herbicide 100 302
Atrazine de-ethyl Herbicide by-product 30 56.8
Bentazon Herbicide 30 12.6
Caffeine Stimulant 55 43.3
N,N-diethyl-3-methylbenzamide (DEET) Insecticide 60 251
Desmethylvenlafaxine Medication (antidepressant) 65 74.7
Dimethenamid Herbicide 45 119
Dimethenamid ethanesulfonic acid Herbicide by-product 35 107
Gabapentin Medication (anticonvulsant) 100 1080
Gemfibrozil Medication (cholesterol mgmt) 35 27.5
Hydrochlorothiazide Medication (diuretic) 55 67.8
Hydroxybupropion Medication (antidepressant metabolite) 40 42.6
Imazethapyr Herbicide 70 198
Lamotrigine Medication (anticonvulsant) 65 85.2
Metformin Medication (antidiabetic) 100 150
Metolachlor Herbicide 65 867
Metolachlor sulfonic acid Herbicide by-product 100 555
Ranitidine Medication (antacid) 42 33.1
Sulfamethoxazole Medication (antibiotic) 55 77.7
Tramadol Medication (opioid, pain reliever) 30 28.2
Apostle Islands National Lakeshore (2014)
Gabapentin Medication (anticonvulsant) 30 13.7
Isle Royale National Park (2015)
Atrazine Herbicide 38 14.6
N,N-diethyl-3-methylbenzamide (DEET) Insecticide 92 119
Indiana Dunes National Lakeshore (2014-2015)
2,4-Dichlorophenoxyacetic acid Herbicide 58 179
Acetochlor oxanilic acid Herbicide by-product 68 105
N,N-diethyl-3-methylbenzamide (DEET) Insecticide 92 122
Gabapentin Medication (anticonvulsant) 58 2790
Imazethapyr Herbicide 42 492
Metformin Medication (antidiabetic) 32 903
Metolachlor sulfonic acid Herbicide by-product 100 1550
Simazine Herbicide 34 3140
Triclopyr Herbicide 39 581

Management Implications

Data from this study will help us to establish a baseline for chemicals of concern in Midwestern national parks and highlight the need to better understand where these chemicals come from, how they get into our surface waters, and what effects they can have on aquatic systems in national parks.

In the meantime, the work continues. We collected samples from inland lakes at Pictured Rocks and Sleeping Bear Dunes national lakeshores in 2016, and we hope to collect samples in 2017 from Voyageurs National Park and Grand Portage National Monument.

For more information: Elliott, S.M., and D.D. VanderMeulen. 2016. A regional assessment of chemicals of concern in surface waters of four Midwestern United States national parks. Science of The Total Environment. DOI: