[Pharmwaste] Contamination in the womb can alter the relative proportion of boys and girls that are born

[DeBiasi,Deborah]

http://environmentalhealthnews.org/newscience/2008/2008-0717hertz-picciottoetal.html

A cohort study of in utero polychlorinated biphenyl (PCB) exposures in relation to secondary sex ratio. 

Hertz-Picciotto, I, TA Jusko, EJ Willman, RJ Baker, JA Keller, SW Teplin and MJ Charles. 2008. Environmental Research 7:37.
July 21, 2008

--------------------------------------------------------------------------------
Synopsis by Dr. Pete Myers
 
Women becoming pregnant in the San Francisco Bay area during the 1960's were a third less likely to give birth to a baby boy if their PCB (polychlorinated biphenyl) levels were relatively high. 

The results adds weight to the growing evidence that contamination in the womb can alter the relative proportion of boys and girls that are born.
   
Context: Around the world, slightly more boys are born than girls. This pattern is remarkably universal, with 51 to 54 boys born for each 50 girls born. Demographers use these data to calculate a population sex ratio, calculated as the number of male births divided by the total number of births.

Some demographers have reported small but significant changes in sex ratio in some countries, for example, in Canada and the US. Fewer boys are being born than expected. Several studies have reported striking local changes in sex ratio associated with chemical exposures, for example in Russian pesticide workers, babies born to men who were exposed to dioxin in the 1976 Seveso (Italy) accident, and babies born to men in Taiwan who were exposed to PCBs while less than 20-years old. All these cases involve fewer boys. Most recently, epidemiologists have observed a dramatic departure from normal in the sex ratio at birth of a First Nations community in SW Ontario. For the 5-year period beginning in 1999, fewer than 35% of live births were boys.

PCBs are a now-banned family of industrial chemical with many different applications, including use as coolants and insulating fluids in electronic equipment like transformers, plasticizers, flame retardants, caulking, wood floor finishes, etc. They are very stable and, through volatilization in warm air, become universally distributed around the world. Peak manufacturing occurred in the 1960s. They were banned beginning in 1973, for use in 'open' sources.' Production was banned in the US in 1977, although uses in capacitors and transformers continued. In 2001 their production was banned globally under the Stockholm Convention on Persistant Organic Pollutants.

PCB toxicity at relatively high doses are overtly toxic. At levels experienced by the general public they are associated with neurological and reproductive harm. Several public agencies, including the US EPA, consider them to be carcinogenic to humans.

What did they do? 
The research team took advantage of the fact that a study of pregnant women and their babies (the Child Health and Development Study) had been carried out in the 1960s in which serum of was stored for later analysis. Conducted by San Francisco Bay area scientists, the study obtained data on about 20,000 pregnancies and has been a rich source of information about how conditions during pregnancy, including contamination, can affect health later in life (e.g., risk of breast cancer). People in the study were representative of a broad cross-section of Bay Area residents, although there were relatively few very poor or very wealthy people. 

For this new analysis, the scientists focused on mothers who had stayed with the research program through an extensive examination when their child reached the age of five. There also had to be enough serum left to carry out chemical analyses for PCBs. Mothers were also left out of this assessment if they birth involved more than one baby (twins, etc.), the baby had severe birth defects, and on the basis of several other factors designed to make sure the assessment focused on normal births and babies. If mothers had had more than one child eligible on the basis of these criteria, only one was used in this study. 

The serum had been frozen since obtained in the late 1960s at a facility of the National Institute of Health. Serum concentrations of PCBs were obtained for 399 women. 

The sex of the babies had been recorded at birth. To explore the relationship between PCB levels and the likelihood of a boy vs. a girl baby, the scientists carried out a series of analysis, beginning with identification of factors that could confound, or confuse, the statistics. These included detailed information about drugs taken during pregnancy and information about how the samples had been stored.

In their analysis, they examined how the chance of giving birth to a boy changed at higher PCB levels compared to lower levels. In a crucial calculation they compared the sex ratio of babies born to women who's PCB levels fell in the lowest (10th percentile) group vs. that of women in the highest (90th percentile).

What did they find? 
The PCB levels they observed in their samples were similar to what scientists were seeing at the time (1960s) across the US. They were significantly higher than those observed today, following the bans that were instituted in the 1970s. The average level of PCBs across all women was 5.4 μg/L (micrograms per liter, or parts per billion). The 10th percentile was 4.7 μg/L and the 90th percentile was 8.7 μg/L.

In their overall assessment of the relationship between PCB level and sex of baby, they found that as PCB levels went up, the likelihood of a boy went down. This overall trend was statistically significant (p < 0.02). For every additional 1 μg/L PCB in serum, the odds of a boy dropped by 7%.

Comparing the women at or below the 10th percentile of PCB levels with those at or above the 90th, they found women with the relatively high levels the likelihood of a boy baby decreased by 33%.
 
What does it mean? 
This study gives additional weight to evidence that contamination in the womb can affect a mother's chances of having a baby boy vs. baby girl. The research is particularly strong because it had a sample size of several hundred births as well as high quality, direct measurements of PCB exposures. 

The exposure levels observed in the study are high compared to today. Thus if these results are indicative of a causal relationship (never possible to confirm with epidemiological studies) then the simplest prediction would be that the chances of having a boy baby should be increasing because PCBs have been decreasing. That is not the case, at least as of the most recent analysis from Canada and the US. 

That suggests at least two possibilites. First, the pattern described here may be an artifact, or second, that other factors are more powerful at influencing sex ratio, so that while PCB levels decline, those other factors are changing in ways that continue to make boys become less likely. The pattern noted above in Ontario suggests that other factors may have a strong effect on sex ratio: PCBs are unlikely to be the causal agent affect this local population because they have been banned for so long, and the environment in which this community resides is beset by many other chemical contaminants. It is entirely plausible, indeed expected, for multiple agents to be affecting common endpoints that are causally involved in setting the likelihood of a male birth.

Resources: 


Child Health and Development Study.

Cohn, BA, MS Wolff, PM Cirillo and RI Sholtz. 2007. DDT and breast cancer in young women: New data on the significance of age at exposure. Environmental Health Perspectives doi:10.1289/ehp.10260

Colborn, T, D Dumanoski and JP Myers. 1996. Our Stolen Future. Chapter 6. To the ends of the Earth.

Davis, DL, MG Gottlieb and JR Stampnitzky. 1998. Reduced ratio of male to female births in several industrial countries: A sentinel health indicator? Journal of the American Medical Association 279:1018-1023.

del Rio Gomez, I, T Marshall, P Tsai, Y-S Shao and YL Guo. 2002. Number of boys born to men exposed to polychlorinated biphenyls. Lancet 360: 143-44.

Mackenzie, CA, A Lockridge and M Keith. 2005. Declining Sex Ratio in a First Nation Community. Environmental Health Perspectives 113: 1295-1298.

Mocarelli, P, PM Gerthoux, E Ferrari, DG Petterson, SM Kieszak, P Brambilla, N Vincoli, S Signorini, P Tramacere, V Carreri, EJ Sampson, WE Turner and LL Needham. 2000. Paternal concentrations of dioxin and sex ratio of offspring. The Lancet 355:1858-1863

US EPA. PCBs.
   Pollution and sex ratio in the news


21 July San Francisco women with higher PCB levels are less likely to give birth to boys. Women becoming pregnant in the San Francisco Bay area during the 1960's were a third less likely to give birth to a baby boy if their PCB levels were relatively high. Environmental Health News.

17 July PCB-exposed women may have fewer boys. Women exposed to high levels of polychlorinated biphenyls, or PCBs, are less likely to give birth to male children, U.S. researchers said. UPI. http://www.upi.com/Health_News/2008/07/16/PCB-exposed_women_may_have_fewer_boys/UPI-41801216241879/

17 July Women exposed to PCBs have fewer male babies. Exposure of women to high levels of polychlorinated biphenyls (PCBs) raises the odds that they will not give birth to male children, according to a study published Thursday in Environmental Health. Xinhua News Agency, China.  http://news.xinhuanet.com/english/2008-07/17/content_8561172.htm

16 July Pollution behind girl child births? Women exposed to high levels of certain kinds of pollutants are less likely to give birth to male children. Indo-Asian News Service, South Asia.  http://timesofindia.indiatimes.com/World/Pollution_behind_girl_child_birth/articleshow/3240580.cms

3 July Extinction threatens more species than thought. The true number of species at risk of extinction is likely to be many times higher than the current official estimate of 16,000, scientists have warned. London Daily Telegraph, England.  



Abstract of study:  http://www.ehjournal.net/content/7/1/37/abstract

Provisional PDF version:   http://www.ehjournal.net/content/pdf/1476-069x-7-37.pdf



Deborah L. DeBiasi
Email:   dldebiasi at deq.virginia.gov
WEB site address:  www.deq.virginia.gov
Virginia Department of Environmental Quality
Office of Water Permit Programs
Industrial Pretreatment/Toxics Management Program
PPCPs, EDCs, and Microconstituents
Mail:          P.O. Box 1105, Richmond, VA  23218 (NEW!)
Location:  629 E. Main Street, Richmond, VA  23219
PH:         804-698-4028
FAX:      804-698-4032

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.dep.state.fl.us/pipermail/pharmwaste/attachments/20080721/85b68b04/attachment-0001.htm