Dust harbors new fire retardants associated with hormone, sperm changes.

What did they do?

Researchers measured the levels of OP flame retardants in house dust collected from the homes of 50 men from infertile couples who were recruited at the Vincent Memorial Andrology Laboratory at the Massachusetts General Hospital.

Dust was obtained by collecting participants’ vacuum cleaner bags. Semen samples were also obtained from participants and parameters associated with male fertility – such as sperm concentration, motility and morphology – were assessed.

In addition, thyroid hormones (free thyroxine, total triiodothyronine and thyroid-stimulating hormone) as well as LH (luteinizing hormone), FSH (follicle-stimulating hormone), estradiol and prolactin were measured in 38 of these men.

What did they find?

The OP flame retardants tris-dichloropropyl (TDPP) and triphenyl phosphate (TPP) were each detected in more than 96 percent of dust samples and concentrations varied widely (by a factor of 100 and 10,000, respectively).

Researchers found that higher dust concentrations of TDPP were related to a decline in the thyroid hormone free thyroxine (T4) in the men. Increasing dust levels of TPP were associated with a decrease in sperm concentration. In addition, higher dust levels of both TDPP and TPP were related with higher levels of the hormone prolactin. No associations were found between OP flame retardants and other hormones or fertility parameters.

What does it mean?

The findings suggest that exposure to OP flame retardants may be related to lower free T4 and sperm concentration as well as higher prolactin hormone levels.

These effects may have important health implications. Thyroid hormones are essential to a number of physiological processes including reproduction, cardiovascular health and neurodevelopment, while prolactin is involved in reproduction and immune system function. Low sperm concentration is related to infertility.

Although participants in this study may not be representiative of the general U.S. population, the high detection frequency of OP flame retardants in household dust suggests that a large proportion of U.S. residents may be exposed. Dust concentrations were similar to those reported for PBDEs in prior U.S. studies and findings suggest that levels of exposure experienced by participants may be sufficient to affect hormone levels and fertility parameters.

Based on their findings, the authors caution that "due to the ubiquity of these compounds in homes and other microenvironments their toxicity potential should be considered more fully, especially as replacements for recently banned or withdrawn PBDE formulations are sought."

Additionally, the results fall in line with suspected health effects of organophosphorus insecticide. Some studies suggest that these chemicals – such as chlorpyrifos – may alter sperm quality, thyroid hormone and prolactin levels in humans. However, the OP flame retardant chemicals are more stable and may persist longer in the environment than their pesticide cousins.

Though this is the first study to evaluate the potential health impacts of exposure to OP flame retardants, it is limited by the fact that exposure was not directly measured but was estimated from dust concentrations.  The results are supported by animal studies that have reported that high doses of OP flame retardants cause adverse reproductive and neurological effects.