Two-decade study reveals link between semen quality and air pollution
23 April 2009
A joint study conducted by Calcutta University and Fertility Clinic & IVF Div. of AMRI Medical Centre, India and Center for Reproductive Medicine, Cleveland Clinic, Ohio, has revealed a decline in semen quality in the last two decades in Kolkata- a major metro city in India.
“It was a first-of-its-kind study in the subcontinent and appeared online in Fertility and Sterility, a research journal of the American Society for Reproductive Medicine,” said a scientist associated with the project.
The examination of 3,729 sperm samples — 1,752 in the 80s (1981-85) and 1,977 in the last decade (2000-07) — revealed a nearly 10 per cent drop in semen volume and a corresponding decline in motility (a measure of the percentage of sperm that can move towards an ovum for fertilization) over 20-odd years.
Alex C. Varghese, the scientific director of the in-vitro fertilization division of AMRI and a co-author of the study, said the changes in infertility patterns were significant because “such a decline has taken place in a very short duration”. According to Dr Alex Varghese, there is a co-relation between urbanisation and growing vehicular pollution and the increasing number of infertility clinics in Asia and the Indian Sub-Continent. That's why it had become imperative to conduct such a study.
“In the last two decades, fertility patterns in the city have undergone tremendous changes and we found a strong correlation between the trend and worsening pollution levels in the city,” said Ashok Bhattacharyya, professor of biochemistry at Calcutta University and a co-author of the paper.
Dyutiman Mukhopadhyay, the first author of the paper, and the other scientists had taken care to avoid “regional variation” in the selection of samples.
According to the report, the root cause of male infertility was regular inhalation of noxious gases belched out by polluting vehicles and the increasing presence of heavy metals such as lead and cadmium in the environment.
The experts attributed the decrease in semen volume mainly to chemicals that adversely affect male sex hormones. Several studies have established that these toxins — released in the air mainly by polluting vehicles — directly affect the functioning of “accessory sex glands” that help produce sperm.
The paper quotes a World Bank study as saying that in 2002 Calcutta was the third most polluted city in the world in terms of concentration of particulate matter. “Transport emissions in Calcutta rose from an estimated 1,825 tonnes per annum in 1970 to 25,550 tonnes in 1990.”
According to Dr. Alex Varghese, increasing seasonal air pollution has also been reported in decreased motility in males in Salt Lake area of Utah in United states. Animal studies indicate DNA mutations in spermatozoa in mice exposed to high air pollution. Some recent European study also indicates high sperm DNA damage due to air pollution without any significant changes in other classical semen parameters.
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