[Paracelsus] Insect spray may lower testosterone levels in men (fwd)

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Subject: [Paracelsus] Insect spray may lower testosterone levels in men

Insect spray may lower testosterone levels in men

Last Updated: 2006-01-11 16:12:57 -0400 (Reuters Health)

By Charnicia E. Huggins

NEW YORK (Reuters Health) - While infertility may

be caused by a number of factors, new study

findings suggest that exposure to nonpersistent,

or short-lasting, insecticides may play a role in

male infertility.

" Environmental exposure to chlorpyrifos or its

metabolite (TCPY) may be associated with reduced

levels of circulating testosterone in adult men, "

lead study author Dr. D. Meeker, of the

University of Michigan, Ann Arbor, told Reuters

Health. " A decline in testosterone throughout a

population could potentially lead to adverse

reproductive health outcomes, " he added.

Until 2000, chlorpyrifos was one of the most

common insecticides used in homes. The

Environmental Protection Agency restricted its

residential use after research revealed it can

affect the central nervous system. Just one year

earlier, however, up to 19 million pounds of the

chlorpyrifos were used in the United States, and

recent investigations suggest that individuals

are still environmentally exposed to the

insecticide, despite EPA restrictions.

The Second National Report on Human Exposure to

Environmental Chemicals found that more than 90

percent of men had detectable levels TCPY in

their urine.

In a previous report, Meeker and his colleagues

also found that higher levels of 1-naphthol (1N)

in men's urine are associated with decreased

concentration and motility of sperm and increased

DNA damage in sperm cells. 1N is a breakdown

product of carbaryl, a lawn and garden

insecticide known as Sevin, and the compound

naphthalene, which is found in cigarette smoke,

diesel fuel and other combustion byproducts.

Meeker and his colleagues from the Harvard School

of Public Health in Boston and the Centers for

Disease Control and Prevention in Atlanta

explored the association between TCPY and 1N, and

reproductive hormone levels in 268 men who were

recruited at an infertility clinic between 2000

and 2003.

Men with higher urine levels of TCPY and 1N had

lower levels of the sex hormone testosterone, the

researchers report in the journal Epidemiology.

They also found that as TCPY levels increased,

testosterone levels decreased.

Higher TCPY levels were also associated with a

decrease in free androgen index, a marker of

lower testosterone concentrations, the report

indicates.

" Although the decrements in testosterone related

to TCPY were relatively small, " Meeker

acknowledged, " they may be of public health

concern because of widespread human exposure

among men. "

The researchers also found some evidence that

higher TCPY and 1N levels are associated with

decreased levels of luteinizing hormone and a

decreased free androgen index, but more studies

are needed to confirm this finding.

If TCPY and 1N are associated with decreased

levels of testosterone and luteinizing hormone,

the hypothalamus and the pituitary gland, rather

than the testes, may be involved in the mechanism

by which certain pesticides affect sperm quality,

Meeker speculates. " But there are several other

potential mechanisms as well, " he said.

According to Meeker, " This is the first human

evidence of an association between chlorpyrifos

or its metabolite (TCPY) and testosterone levels,

so other studies would be needed to substantiate

our findings. "

SOURCE: Epidemiology, January 2006.

Copyright © 2006 Reuters Limited.

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