Published online in Human Reproduction, Europe's leading reproductive medicine journal, the study found that women who had higher levels of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) in their blood took longer to become pregnant than women with lower levels.
The UCLA researchers used data from the Danish National Birth Cohort to assess whether levels of PFOS and PFOA in pregnant women's plasma were associated with a longer time to pregnancy. A total of 1,240 women were included in their analyses.
Blood samples were first taken between 4 and 14 weeks into the pregnancy so that concentrations of PFOS and PFOA could be measured. The researchers also interviewed the women at around the 12th week of pregnancy to find out whether the pregnancy was planned or not and how long it took them to become pregnant. Infertility was defined as a time to pregnancy of longer than 12 months or a situation in which infertility treatments were used to establish the pregnancy, and the results were adjusted for potential confounding factors such as age, lifestyle and socioeconomic status.
The level of PFOS in the women's plasma ranged from 6.4 nanograms per milliliter (ng/ml) to 106.7 ng/ml, and from less than 1 ng/ml to 41.5 ng/ml for PFOA.
The researchers divided the women's levels of PFOS/PFOA into four quartiles and found that, compared with women with the lowest levels of exposure, the likelihood of infertility increased by 70 to 134 percent for women in the higher three quartiles of PFOS exposure and by 60 to 154 percent for women in the higher three quartiles of PFOA exposure.
"Perfluorooctanoate and perfluorooctane sulfonate were considered to be biologically inactive, but recently, animal studies have shown that these chemicals may have a variety of toxic effects on the liver, immune system and developmental and reproductive organs," said UCLA researcher Chunyuan Fei, the study's first author. "Very few human studies have been done, but one of our earlier studies showed that PFOA, although not PFOS, may impair the growth of babies in the womb, and another two epidemiological studies linked PFOA and PFOS to impaired fetal growth."
"As far as we know, this is the first study to assess the associations between PFOA and PFOS levels in plasma with time to pregnancy in humans," said principal investigator Jørn Olsen, chair of the department of epidemiology at the UCLA School of Public Health. "We are waiting for further studies to replicate our findings in order to discover whether the chemicals should be added to the list of risk factors for infertility."
In addition to being found in household goods, PFCs, the class of chemicals to which PFOS and PFOA belong, are used in manufacturing processes involving industrial surfactants and emulsifiers. They persist in the environment and in the body for decades.
The researchers believe that although they measured the PFOS/PFOA levels after pregnancy was established, these levels probably did not change significantly from the time before pregnancy. Men's sperm quality could also be affected by PFCs and might, therefore, contribute to the associations between PFC levels and time to pregnancy, since couples would tend to be sharing the same lifestyles and have similar exposures. However, the researchers did not have data on PFC levels in fathers.
"Studies on sperm quality and PFOA/PFOS are certainly warranted," Olsen said.
The researchers say the biological mechanisms by which exposure to PFOS and PFOA might reduce fertility are unknown, but PFCs may interfere with hormones that are involved in reproduction.
"Our data showed that higher proportions of women reported irregular menstrual periods in the upper three quartiles of PFOA and PFOS, compared with the lowest, and so this could indicate a possible pathway," Fei said.
Biofilm discovery suggests new way to prevent dangerous infections
23.05.2017 | University of Texas at Austin
Another reason to exercise: Burning bone fat -- a key to better bone health
19.05.2017 | University of North Carolina Health Care
Staphylococcus aureus is a feared pathogen (MRSA, multi-resistant S. aureus) due to frequent resistances against many antibiotics, especially in hospital infections. Researchers at the Paul-Ehrlich-Institut have identified immunological processes that prevent a successful immune response directed against the pathogenic agent. The delivery of bacterial proteins with RNA adjuvant or messenger RNA (mRNA) into immune cells allows the re-direction of the immune response towards an active defense against S. aureus. This could be of significant importance for the development of an effective vaccine. PLOS Pathogens has published these research results online on 25 May 2017.
Staphylococcus aureus (S. aureus) is a bacterium that colonizes by far more than half of the skin and the mucosa of adults, usually without causing infections....
Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.
The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
24.05.2017 | Event News
23.05.2017 | Event News
22.05.2017 | Event News
26.05.2017 | Life Sciences
26.05.2017 | Life Sciences
26.05.2017 | Physics and Astronomy