Phthalates make plasticizers infertile medicine transparent

Phthalates: make softeners infertile?Phthalates make plasticizers infertile medicine transparent

Phthalates make plastics soft and pliable. The chemicals are a component of many plastic products, for example PVC floor coverings, synthetic leather or plastic toys. The plasticizers are also found in paints, varnishes, deodorants, nail polish and body lotions. Some drug manufacturers even use them as a coating for their medicines [9,11].

Infertility in animals and humans

For the industry, phthalates have many positive properties. But what about health?? Experiments have shown that phthalates affect fertility in laboratory animals [12]. Although the results of studies on laboratory rats can be. Mice not readily transferred to humans. Nevertheless, they are an important indicator of potential risk.

So do phthalates affect sex hormones and fertility in female and male? This ie is important because many different products contain plasticizers and phthalates can be detected in the bodies of most people [11]. We wanted to know if these levels are enough to cause infertility in humans as well.

Plasticizers and semen quality

According to previous studies, the amount of individual phthalates in men's bodies could be enough to affect the quality of their sperm cells [1-6]. So the plasticizers may make sperm less mobile or damage their genetic material. This could limit men from fathering a child.

In most studies men are described, who were connected with a partner and whose child desire remained so far unfulfilled. Study results showed that men's semen was particularly often of low quality when the men had high levels of phthalates in their bodies. However, this observation is not proof that softeners were really to blame. There may also be other reasons for infertility, such as exposure to other chemicals or smoking, alcohol, advanced age, or the fact that the last ejaculation occurred several days ago.

Another limitation of the significance: it has not been proven that the detected poorer semen quality is not sufficient to father a child. This means that whether men with high levels of plasticizers in their bodies are actually less likely to become fathers than men with low levels of phthalates is conceivable, but still unresolved. Only future studies can answer this question.

Getting pregnant more difficult?

Plasticizers are not only suspected of reducing men's ability to conceive. It is also conceivable that the chemicals affect women's fertility. However, this has not yet been sufficiently researched.

We could only find two studies on this. In one, a Danish scientific team measured phthalate exposure in about 200 women who were planning their first pregnancy [7]. However, problems with the measurement and several missing data ensured that the results of this study are not reliable. Whether phthalates make it more difficult for women to become pregnant can only be proven by more rigorously conducted studies on a larger number of participants.

In the second study, a research team from the United States investigated whether there was a relationship between the number of fertilizable eggs a woman had and the amount of phthalates in her body [8]. Whether women with high phthalate levels had greater problems getting pregnant, however, cannot be reliably determined from the study.

Background softener

Plasticizers are not firmly bound in plastics; that is, phthalates can escape over time [9]. They either slowly evaporate or can pass from food packages directly into the food wrapped with them. During daily use of plastics – for example when walking over a PVC floor – tiny plastic particles can rub off. These particles eventually find themselves in household dust – such as on bookshelves and other nooks and crannies in our homes.

A study by the German Federal Environment Agency showed that we consume phthalates most frequently with food [10]. Small children additionally swallow larger amounts of it because they put dusty things or objects made of plastic into their mouths.

Partially banned in the EU

Based on previous research in laboratory animals and humans, the EU classifies three commonly used phthalates as toxic to reproduction [9]:

– DEHP (di(2-ethylhexyl) phthalate) – DBP (dibutyl phthalate) – BBP (benzyl butyl phthalate)

Because young children are particularly at risk, these chemicals are not allowed in baby products or toys in the EU. However, they are also banned in cosmetic products or varnishes and paints [9]. For example, DINP. DIDP toxic to the liver above a certain level.

Another phthalate, namely DPHP (di(2-propylheptyl)phthalate) can damage two vital endocrine glands in experimental animals: the thyroid gland and the pituitary gland [9]. This substance is not prohibited.

The studies in detail

Animal studies provide clear evidence that some phthalates can promote infertility [12]. We wanted to know if the amounts of phthalates that people are exposed to in everyday life are sufficient to do this. Therefore, we searched medical databases for studies to learn more about possible effects on male and female fertility.

Cross-sectional seed quality studies

In our extensive search for studies on male infertility, we only found studies on semen quality. A Chinese scientific team summarized the results of all those studies published on this topic until 2014 [1].

These studies mostly took the form of cross-sectional studies. This means that both phthalate exposure and semen quality of the men were measured at only one point in time – a snapshot, so to speak. This type of study has several drawbacks: It is conceivable that phthalate levels and seed quality fluctuated over time. However, cross-sectional studies cannot clarify how sperm quality and phthalate levels evolved before and after measurement, and whether this evolution was similar.

Furthermore, the data collected in the studies cannot prove that there is a real connection, i.e. that high phthalate levels have a negative effect on semen quality. Alternative explanations may be possible, such as exposure to other chemicals, but also smoking, alcohol, older age, or prolonged sexual abstinence. In addition, mostly only men who had been diagnosed with a fertility disorder by a male or female doctor were studied. Whether the putative link between phthalates and semen quality also exists for men without this diagnosis is less certain.

In our search for more recent studies, we found three other cross-sectional studies whose results pointed in the same direction [2,4,5].

Longitudinal studies on semen quality

However, we also found two studies in which the values were measured at two different time points – so-called longitudinal studies [3,6]. In theory, this study design is more informative than cross-sectional studies. Men a semen sample at the beginning of the study. Another one month after. The research team compared both semen samples with phthalate levels from just one urine sample taken at the start of the study. This means that the significance is no higher than in the cross-sectional studies mentioned above.

In another study [6], a science team examined male students at a Chinese university campus. The drinking water at this campus was heavily contaminated with phthalates. One month after the study began, participants moved to a new campus where phthalate levels in drinking water were lower. The team measured phthalate levels and semen quality of participants before and after relocation. It found that, on average, sperm quality was lower in participants with high phthalate levels. After the move, the quality of sperm improved and phthalate smears decreased.

Although measuring phthalate levels and semen quality twice makes the results somewhat more meaningful than cross-sectional studies, there are some unanswered questions in this study. For example, the science team only partially clarified the extent to which participants with low semen quality differed from participants with high semen quality. So, while students had to indicate at the start of the study whether they smoked, drank alcohol, how old and heavy they were, and how long they had been abstinent before providing the semen sample. Other factors, such as healthier lifestyles, disease, or stress, may also have affected semen quality. However, they were not part of the survey.

Time to pregnancy

Two science teams [7,8] reviewed whether high exposure to plasticizers affects fertility in women. For one of these studies [7], 229 Danish women froze once a month on 10. cycle day their morning urine. A research team compared the sample from the first month with that from the month in which pregnancy occurred. In this way, they wanted to investigate whether the amount of phthalate degradation products was particularly high when pregnancy was a long time coming.

The results are not very reliable for several reasons. It is possible that the uncontrolled freezing and storage of the urine samples in the freezer at home has falsified the concentration of the sensitive phthalate degradation products. In addition, the research team did not investigate whether some participants may not have become pregnant due to disease. It is also unclear whether this was caused by men. The fact that the research team excluded 77 women from the study because they had already become pregnant in the first month further diminishes the significance of the study.

The second study [8] was conducted in a low-impact cross-sectional design. A research team examined the number of fertilizable eggs in 215 women and found an association between phthalate exposure in urine and low egg reserve. However, the study does not prove whether high levels of plasticizers are actually the cause of a low reserve of fertilizable eggs. Thus, it cannot be ruled out that in reality entirely different causes are responsible.

[Updated on 12. 12. 2017, originally published on 10. 1. 2013. A search for new research changes our assessment.]

Information about the scientific studies

[1] Cai u.a. (2015)
Type of study: systematic review Studies analyzed: 14 cross-sectional studies Research question: Is there a relationship between high phthalate levels in blood or urine of men and sperm quality?? Conflicts of interest: none according to authors

Cai H, Zheng W, et al. Human urinary/seminal phthalates or their metabolite levels and semen quality: A meta-analysis. Environ Res. 2015 Oct;142:486-94. (summary of the review)

[2] Den Hond (2015)
Study type: case-control with cross-sectional design Participants: 163 men Research question: is there an association between high levels of phthalates in men's blood or urine and sperm quality? Conflicts of interest: none according to authors

Den Hond E, Tournaye H, et al. Human exposure to endocrine disrupting chemicals and fertility: a case-control study in male subfertility patients. Environ Int. 2015 Nov;84:154-60. (Study abstract)

[3] Bloom u.a. (2015)
Study type:Partial analysis of a cohort study Participants: 501 men whose partners have problems getting pregnant Research question: Is there a correlation between high phthalate levels in men's urine and sperm quality?? Conflicts of interest: none according to the authors

Bloom MS, Whitcomb BW, et al. Associations between urinary phthalate concentrations and semen quality parameters in a general population. Hum Reprod. 2015 Nov;30(11):2645-57. (full length study)

[4] Wang u.a. (2016)
Study type: cross-sectional study Participants: 1040 men Research question: is there a relationship between high levels of phthalates in men's blood or urine and sperm quality? Conflicts of interest: none according to authors

Wang YX, Zeng Q, et al. Phthalate exposure in association with serum hormone levels, sperm DNA damage and spermatozoa apoptosis: A cross-sectional study in China. Environ Res. 2016 Oct;150:557-65. (Study abstract)

[5] Thurston u.a. (2016)
Study type: cross-sectional study Participants: 420 men whose partners were pregnant Question: Is there a relationship between high phthalate levels in fertile men and sperm quality? Conflicts of interest: none according to authors

Thurston SW, Mendiola J, et al. Phthalate exposure and semen quality in fertile US men. Andrology. 2016 Jul;4(4):632-8. (full length study)

[6] Chen u.a. (2017)
Study type: Prospective cohort study Participants: 796 students in China Research question: Is there an association between high levels of phthalates in men's blood or urine and sperm quality??: Conflicts of interest: none according to authors

Chen Q, Yang H, et al. Phthalate exposure, even below US EPA reference doses, was associated with semen quality and reproductive hormones: Prospective MARHCS study in general population. Environ Int. 2017 Jul;104:58-68. (Summary of the study)

[7] Thomsen u.a. (2017)
Study type: Prospective cohort study Participants: 229 women planning their first pregnancy Question: Do women with higher urinary phthalate levels become pregnant later than women with lower levels?? Conflicts of interest: none according to authors

Thomsen AM, Riis AH, et al. Female exposure to phthalates and time to pregnancy: a first pregnancy planner study. Hum Reprod. 2017 Jan;32(1):232-238. (Summary of the study)

[8] Messerlian u.a. (2016)
Study type: cross-sectional study Participants: 215 women from a fertility clinic Research question: Is there a relationship between ovarian reserve and phthalate concentration in the body?? Conflicts of interest: none according to authors

Messerlian C, Souter I, et al. Urinary phthalate metabolites and ovarian reserve among women seeking infertility care. Hum Reprod.

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