SAN PEDRO, Laguna—The water of Laguna Lake is contaminated with a high level of female sex hormones, about 10 times higher than normal, alarming researchers over a possible threat to the lake’s fish population, a recent study showed.
The presence of estrogen (E2), a primary female sex hormone, in the water was manifested in the male species of the common carp that developed reproductive abnormalities only after a month of exposure to the lake water, according to a University of the Philippines Los Baños (UPLB) study done in August last year and released this month.
Such changes include the delayed maturation of the germ cells, growth of lesions in the fish’s testis and the development of vitellogenin, an egg yolk protein precursor that is normally found only in the female fish, said the study conducted by Dr. Michelle Grace Paraso, an associate professor at the College of Veterinary Medicine in UPLB.
Test results
The research, titled “Estrogenic Disruption in Male Common Carp (Cyprinus carpio Linnaeus) Introduced to the East and West Sites of Laguna de Bay,” was funded by the Southeast Asian Regional Center for Graduate Study and Research in Agriculture (Searca) for Paraso’s doctoral dissertation and was presented in a Searca seminar on Aug. 3 at UPLB.
Paraso said 28 male common carps, kept in fish cages, were exposed to the lake water in the east bay (areas covered by the towns of Sta. Cruz and Paete in Laguna) and in the west portion (Sta. Rosa and Calamba cities) of Laguna Lake. The fish were later examined and compared with 12 other carps kept at the UPLB Limnological Research Station.
After taking blood and tissue samples, about 25 percent of the carps from Laguna Lake showed “characteristics of feminization,” while none of those from the research pond developed abnormalities, Paraso told Inquirer in a phone interview Friday.
Sources of pollution
She said she believed the abnormal fish ingested estrogen through animal and human feces and urine, which carried the hormone excretions, that found their way into the lake’s water. While both female and male species produce estrogen, the male excretes only a small amount of this hormone, Paraso explained.
The lakeshore areas, Paraso described, were highly residential but with poor sewage systems, except for the area in Paete, where the residents are engaged in backyard agriculture.
But what even more startled Paraso was that the level of estrogen in Laguna Lake was 300-400 nanograms per liter as revealed in a water sampling test.
Comparing it with the results of researches abroad, she said it was “ten times higher” than the estrogen level found in a river in Vietnam that was only 10 nanograms per liter, or in Taiwan which was only 14 nanograms per liter, or in Japan at 27 nanograms per liter.
‘Is this true?’
“I myself was surprised. I was like, ‘is this true?’” she said.
Laguna Lake is being tapped as a viable source of potable water for Metro Manila and supplies fish products, primarily bangus (milkfish) and tilapia, to consumers.
Paraso said while science has yet to prove the adverse effects of estrogen pollution on fish and fish consumers, some areas in the United States, Japan and Europe attribute the decline of male sperm count, infertility and cases of prostate cancer to exposure to high levels of estrogen.