Prenatal exposure to flame retardant is associated with increased risk of male genital anomalies.
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Small CM, JJ Decaro, ML Terrell, C Dominguez, LL Cameron, J Wirth and M Marcus. Maternal exposure to a brominated flame retardant and genitourinary conditions in male offspring. Environmental Health Perspectives doi: 10.1289/ehp.0800058. |
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| Edward Melendez, Flickr. |
| Boys exposed to certain flame retardants in the womb were more likely to have genital problems, study finds. |
Researchers report a higher risk of genital anomalies in boys and men exposed before birth to polybrominated biphenyl (PBB) flame retardants. Although no longer used, the effects of exposure to PBBs are of concern due to their similarity to currently used flame retardants, their long half-life and their ability to cross the placenta. The children of mothers who had the highest exposures also had a greater risk for urinary tract or genital problems. The study followed a group of women who consumed contaminated meat and milk almost 40 years ago after cattle were accidently fed a PBB mixture rather than a feed supplement with a similar name.
Context
Flame retardants are chemicals that are commonly added to electronics, such as cell phones and computers, as well as furniture and mattresses, to reduce their chance of catching on fire and to slow down their burning rate if they do catch on fire.
Some flame retardants, such as polybrominated biphenyls (PBBs) have been shown to cross the placenta. PBBs can also stay in the body for decades. A mother's current and prior exposure to these chemicals may result in exposure to her fetus, too.
Though no longer used, health effects of PBBs are of concern because they are similar to another fire retardant called polybrominated diphenylethers (PBDEs). PBDE use has dramatically increased in recent years, possibly due to more stringent fire safety rules. PBDEs contaminate the environment and have been found in human breast milk, urine and blood in the United States, Canada, Europe, Asia and even in Inuits, who live in the Arctic.
Studies suggest that the rates of male genital anomalies such as undescended testes (cryptorchidism) and abnormal positioning of the urethra (hypospadias) have been increasing in the United States and other developed countries.
Some scientists have proposed that the increase may be due to chemical exposures that interfere with hormones, such as estrogen and testosterone. Male effects–called testicular dysgenesis syndrome–may result from abnormal testes cell development, leading to lower testosterone production and genital and urinary tract development abnormalities.
What did they do?
Researchers examined 464 males whose mothers were exposed to PBBs in 1973 and 1974 through contaminated meat and dairy products when NutriMaster, a cattle feed supplement, was accidentally replaced with the flame retardant FireMaster.
The mothers were part of a cohort of about 4,000 exposed individuals who have been followed since the incident by the Michigan Department of Community Health for long-term health monitoring.
PBB levels were measured in the blood of mothers when they enrolled in the study. Samples were collected before birth for 393 sons. The sons' genital conditions were assessed through the mother, the mother and son or the son via questionnaires and telephone interviews. Male participants ranged in age from 5 to 30 years old.
What did they find?
Researchers found that sons of mothers with high PBB blood concentrations before the sons' birth (more than 5 parts per billion) had 3 times the risk of having genital conditions compared with boys whose mother had a lower exposure (less than 1 part per billion). The problems included hernias, hydroceles, cryptorchidism, hypospadias and varicocele.
Associations were strongest for sons with hernia – a protrusion of the small bowel into the scrotum – or hydrocele – an accumulation of fluids in the scrotum.
The risk of having one of these two conditions increased with exposure and was 6 times higher in sons of highly exposed mothers compared with sons of mothers with a low exposure.
What does it mean?
This study is the first to report associations between prenatal exposure to PBBs and the risk of several types of male genital anomalies.
The authors conclude that "in the present study in utero PBB exposure was associated with reports of hernia and hydrocele. This suggests endocrine disruptors may predispose to a wider variety of conditions than currently acknowledged."
The two problems with the strongest associations – hernia and hydrocele – can be corrected by surgery and both can form either before or after birth. Hernias may result in intestinal obstruction and other complications including hydrocele, which, if untreated, may continue to grow.
Findings in this study are analogous to those obtained by a previous study that found higher concentrations of PBDEs in the breastmilk of mothers of boys with cryptorchidism relative to mothers of boys with no genital anomaly.
The present study was limited by the fact that participants knew their PBB blood concentrations when they were asked about genital anomalies. Individuals who had high levels of exposure may thus have been more likely to remember a genital condition, especially if minor, than those with low exposure.
In addition, authors had limited information on smoking during pregnancy and were therefore unable to verify whether the associations that they reported may have been due to this habit, which has been found to cause birth defects.
ResourcesFries, G and RD Kimbrough. 1985. The PBB episode in Michigan: An overall appraisal. Critical Reviews in Toxicology 16 (2):105-156. Main KM, H Kiviranta, HE Virtanen, E Sundqvist, JT Tuomisto, J Tuomisto, T Vartiainen, NE Shakkebaek and J Toppari. 2007. Flame retardants in placenta and breast milk and cryptorchidism in newborn boys. Environmental Health Perspectives 115(10):1519-1526. PBBs (polybrominated biphenyls) in Michigan (PDF). Michigan Department of Community Health. Polybrominated Biphenyls and Polybrominated Diphenyl Ethers. 2004. Agency for Toxic Substances and Disease Registry. Toppari J, M Kaleva and HE Virtanen. 2001. Trends in the incidence of cryptorchidism and hypospadias, and methodological limitations of registry-based data. Human Reproduction Update 7(3):282-286. ToxFAQs for polybrominated biphenyls (PBBs). 2004. Agency for Toxic Substances and Disease Registry. |
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