June 2022, ScientificAmerican.com 21
Source: “Pharmaceutical Pollution of the World’s Rivers,” by John L. Wilkinson et al.,
in^ Proceedings of the National Academy of Sciences USA,
Vol. 119; February 22, 2022
Graphic by Amanda Montañez
Africa
Asia
KEY
Europe
North America
South America
Oceania Antarctica
Circle size shows mean cumulative concentration
of pharmaceuticals found in each campaign
Color shows country’s
income level
(per the World Bank)
50,000
nanograms
per liter (ng/L)
5,000 500 50
Low
Lower-middle
Upper-middle
High
Not listed
Each circle represents
a sampling campaign
consisting of water
collection from sites
within a city, town
or local area. Most
campaigns included
5 to 11 sites.
Lahore, Pakistan
70,700 ng/L
La Paz, Bolivia
68,800 ng/L
Addis Ababa,
Ethiopia
51,300 ng/L
Bukavu,
Democratic Rep.
of Congo
35,500
Tunis, Tunisia
39,700
Hyderabad, India
46,700
Yerevan,
Armenia
32,000
20,500 15,700
Montevideo,
Uruguay
Madrid, Spain
Dallas, Texas
Las Vegas,
Nevada
Sofia, Bulgaria
Luxembourg City,
Luxembourg
Buenos Aires,
Argentina
17,100 ng/L 12,700 10,700
10,200 5,170
San José,
Costa Rica
25,800 ng/L
In Barisal, Bangladesh, concentrations of the antibiotic metronidazole were
over 300 times the threshold for development of antimicrobial resistance.
In Nairobi, Kenya, high pollution levels
were attributed in part to trucks emptying
waste from septic tanks into local rivers.
The Rio Seke in La Paz contained 227,000 ng/L of paracetamol (known in the U.S.
as acetaminophen), the highest concetration of any chemical measured in the study.
ENVIRONMENT
Mainstream
Drugs
Many of the world’s rivers are
coursing with pharmaceuticals
For more than 20 years scientists have
known that the drugs we take, for mala
dies ranging from headaches to diabetes,
eventually make their way into our
waterways—where they can harm the
ecosystem and potentially promote anti
biotic resistance.
But most research on pharmaceutical
contaminants has been done in North
America, Europe and China and has exam
ined just a small subset of compounds.
The studies also use a variety of sampling
and analysis methods, making it hard to
compare results. Such limitations mean
scientists may be missing a big piece of
the pollution puzzle.
A new paper published in the Proceed-
ings of the National Academy of Sciences USA
provides a more comprehensive look. A
network of 127 scientists sampled 258 rivers
in 104 countries for 61 different chemicals,
producing “a sort of ‘pharmaceutical finger
print’ of nearly half a billion people across all
the world’s continents,” says study lead
author John L. Wilkinson, an environmental
chemist at the University of York in England.
Many of the most drugpolluted rivers
were in Africa and Asia, “in areas and coun
tries that have been largely forgotten by the
scientific community” on this issue, Wilkin
son says. Waterways with the biggest phar
maceutical concentrations also tended to
be in lowermiddleincome countries; the
authors say this could stem from improved
medication access in places that still lack
sufficient wastewater infrastructure.
Four compounds—caffeine, nicotine,
acetaminophen and cotinine (a chemical
produced by the body after exposure to
nicotine)—showed up on every continent,
including Antarctica. Another 14, including
antihistamines, antidepressants and an
antibiotic, were traced on all continents
except Antarctica. Some drugs were
detected only in specific places, such as
an antimalarial found in African samples.
Overall, the study shows that “more
of this kind of global assessment of aquatic
pollution” is needed, particularly for other
chemicals that pose more of a human health
risk, says Elsie Sunderland, a Harvard
University environmental scientist who
was not involved with the new research.
It also suggests, she adds, that “we need
wastewater treatment.”
— Andrea Thompson