Shanna Swan’s recent book has a comprehensive name: Count Down: How our Modern World Is Threatening Sperm Counts, Altering Male And Female Reproductive Development And Imperiling The Human Race. “It is no longer business as usual when it comes to human reproduction,” she writes. “We are living in an age of reproductive reckoning that is having reverberating effects across the planet.” In 2017, the environmental and reproductive epidemiologist documented how the average sperm count among men in the west had more than halved in nearly 40 years.
In her book, she talks about how chemicals in our environment are endangering the sexual health of both men and women, thereby affecting their ability to conceive naturally. In recent years, she explains, we have witnessed an increasing number of babies born with smaller penises, higher rates of erectile dysfunction and girls hitting puberty early. This is just the beginning, she says. Excerpts from an interview:
Q/Your study on low sperm count and your book have created quite a stir. Did it lead to any policy overhaul on chemical exposure in the US?
A/ No. It is difficult, but not impossible. There are many companies now that are expressing commitment to making safer products. We need more public pressure to press for change and move away from these hazardous chemicals. We need chemicals that are not hormonally active and this is difficult because there are many hormones in the body and testing the chemicals to be free of hormonal action is difficult. But I think we can do it.
Q/You say that the sperm count could hit zero by 2045.
A/ What we know is that sperm count concentration has been decreasing dramatically, and hypothetically it could hit zero in 2045. However, hitting zero would mean that the median sperm count would be zero in 2045. Now, is that possible? No, because we cannot have negative sperm [count], which means we can come arbitrarily close to it but we cannot go below it. In western countries, at the end of the study period, the median sperm count was 47 million per millilitre. This is extremely low and it is about 52 per cent lower than it was 39 years ago. So, it is showing evidence of slowing down. The way you look at that is you go back by each decade and if decade after decade it is slowing down, then it should become less till it flattens, and I believe that will happen. Also, 47mpm is very low because it is close to 40mpm, which is the point at which it takes longer and longer to get pregnant. As the sperm concentration drops below 40mpm, the couple will not be able to conceive without assisted reproduction.
Q/Can your meta-analysis on sperm count be applied to Asian countries as well?
A/ When we did this study… there were very few non-western studies. First, because [of the size, demography] of the population. Second, the infrastructure required to carry out these studies. Nevertheless, I am sure India has got the knowledge and the ability to count sperm. But they have not published many studies. That is the problem. But I am sure that just as in the west, men in India do not get their sperm count tested and do not know what their sperm count is. Also, there is a lack of awareness. Sperm count is not just an indicator of reproductive health, but a low sperm count is an indicator of the presence of disease—heart disease, diabetes and reproductive cancers. And, they die younger. So, just like one finds out one’s cholesterol and blood pressure levels, one must get his sperm count routinely checked.
Q/You speak of endocrine-disrupting chemicals (EDCs), specifically phthalates that are added to plastics, cosmetics, cookware coatings and food wrappers. You also speak of bisphenols and pesticides. We are exposed to these in India as well. How can such exposure make us infertile?
A/ They are not chemically bound to the products. That means they can leave. For example, if you look closely at premature babies in a hospital or a paediatric ward, their food comes in through tubes; oxygen too. You can show that the number of tubes to which a baby is connected is directly related to the amount of phthalates in her urine. This is proof that phthalates in the tube leave the tube, enter the nutrients going into the baby and go into the urine, because these are water soluble and you can measure it. That is an example of how food gets contaminated.
Another way… is when an expecting mother eats food that has phthalates in it…. It goes into her bloodstream, crosses the placental barrier and gets into the foetus and affects its development…. And we have shown that by measuring what is in the woman’s urine, we know how much phthalates or bisphenols or pesticides are in her body and we know that that level of these chemicals in her body affect the development of the child at birth and afterwards. And we can show that link.
They also come in through the air we inhale. For example, the phthalates present in hair spray. Chemicals in fabrics, wall coverings and coatings—they get into the air and dust we breathe in. They can also come in through our skin by way of chemicals added to personal care products and cosmetics. The chemicals increase the absorption through our skin; they are put in it for that reason.
So, they come into our bodies in every possible way—inhalation, dermal and ingestion. And, we get them from everything in our household. Exceptions are ceramics, glass, metal or any uncoated products.
Q/Do you think the presence of these chemicals is higher in developing countries than in developed ones?
A/ I do know that the levels are higher in disadvantaged communities and in communities that are poorer, eat poor products or are less likely to eat unprocessed food. Those living near freeways and dumps, too, are more likely to be impacted. The proximity to pollution definitely increases the burden. So yes, it is likely that the levels are higher in developing countries.
I define fertility rate as the number of children born to a couple. So, when that is 2.1, that is what we call replacement. If a couple has two or over two children, then they will replace themselves. But if it goes much below 2.1, they are no longer replacing themselves and the population is declining. In some Asian countries, they are very close to 1.0, which is extremely low. I think Korea had the lowest ever reported fertility rate of [0.84]. As per the World Bank fertility data, in India you will see that the fertility rate declined from 5.9 in 1960 to 2.2 in 2018. That is a faster decline than that seen in the world (from 4.98 to 2.43) in the same time.
Q/But the decline in the number of births could also be because people are choosing to have fewer children or have them later.
A/ But the problem is that young women are having lower fertility than their grandmothers did when they were at the same age. So, it is not just an age question. Secondly, if you look at other non-human species that are also suffering from decline in fertility, we know that they are not choosing to have children later or to have fewer children. I strongly feel that the same forces that are affecting those species are also affecting us…. It can be choice, but it is definitely not only choice.
Q/Are EDCs increasing the risk of miscarriage and affecting the quality of eggs and egg reserves?
A/ Yes, they increase the risk of miscarriage by affecting the quality of the eggs, but also through men. Fifty per cent of miscarriages and infertility issues is attributable to men…. The problems in a man and his exposures at the time of conceiving a child contribute to this as well.
Q/There is a link between the exposure to phthalates and decrease in libido and a rise in sex fatigue.
A/ Phthalates lower testosterone, a hormone which is present in both men and women and one that is crucially linked to libido. So, when one goes to watch an exciting film, for example, or indulge in a fight or a sports event, their testosterone goes up. So, it kind of fluctuates over the course of the day. It is reduced by both prenatal and adult exposure to these chemicals….
We did a study in pregnant women, and looked at phthalate levels in their urine. Then we asked them about their sexual satisfaction and frequency of sex. Higher the phthalate levels, the lower the sexual satisfaction. In a study in China, men who were manufacturing products with bisphenols had more erectile dysfunction and lower libido. Now, how do these act in the body? They certainly act through the brain. Because these chemicals are related to the sexual differentiation of the brain. So, they have the ability to alter the hormonal balance between testosterone and oestrogen, which, when thrown off, [leads to] lower sexual satisfaction, lower libido and erectile dysfunction. Also, so many young men are now getting testosterone supplements, especially at a time when we know that worldwide testosterone levels have been dropping. So, to see it all together in one frame, we have sperm count declining, fertility declining, testosterone is declining and so obviously the interest in sex goes for a toss.
Q/How about non-chemical factors contributing to a decline in fertility?
A/ Absolutely. Stress is the biggest one of them. As far as sperm count and fertility are concerned, smoking is an important factor. Alcohol, obesity and hormonal levels are very tightly connected to body fat, and impact the semen quality in men and menstrual function in women. Then we have diet and quality of food. These are all in the huge category we term as lifestyle factors. Between the chemical and non-chemical factors, it is not easy to [quantify their contribution to fertility decline]. But during pregnancy and early development of foetus, impact on the foetus is unquestionably through chemicals as they are predominant. However, many lifestyle factors, too, involve a high exposure to chemicals. Most of these lifestyle-related factors are reversible. But the damage [done while in the] mother's womb will never be fixed. Hence, those exposures are the most important.
Q/In the book, you talk about a certain pesticide used on pineapples and its effect on sperm count.
A/ It pertained to the use of dibromochloropropane (DBCP) in the harvesting of pineapple. In each of the countries where it was used, including South America and Israel, it was found by workers and their families that they were not having children. And when the men got tested, it was found that they had zero sperm. When they stopped using it, in a couple of months the sperm count returned.
Q/In India, DBCP was banned in 2019. But a ban on one chemical will lead to the rise of the other. Can we afford to live in a chemical-free world?
A/ It is possible to create chemicals that can be helpful to us and that will not harm our hormones or reproductive health of all species. Also, people do not believe that the chemicals are harmful. They do not feel personally threatened. As the number of couples who cannot have a child increases, and as people become aware of effects of chemicals on their libido, they will start taking action.
Q/So, should we look for labels such as BPA-free? How do we cut the exposure to chemicals?
A/ These labels are tricky. When people demanded Bisphenol A free labelled baby bottles, manufacturers took BPA out of those products and labelled them as such…. The product might say BPA free, but add other forms of bisphenols, such as Bisphenol F and Bisphenol S. And that happens with phthalates as well. So, do not trust the product. I have a checklist of things one can do in my book.
Q/How do you keep yourself away from these chemicals?
A/ I am lucky because I live near a farmer’s market in New York City, so I have the option to shop organic and buy fresh food. I try to not use plastics, especially for storage, wrapping and cooking food. Cooking is more dangerous because when food gets warm, there are more chemicals released into the food. For cosmetics, I check the labels on products I apply on my face and go to websites that I have listed in my book…. But it is not easy because EDCs may also come in by way of Teflon-coated pans. I only use iron for cooking. So, you need to see the specifications on the product and do more research to convince yourself that the product is safe.
Q/You say that a time will come when many couples will need to turn to assisted reproductive technology and eggs and sperms that are created from other cells in the laboratory.
A/ That is the last option, and that time will come because very few men have good enough sperms to donate to sperm banks…. There was one known study in China where a major sperm bank had to close because there were not enough men who could donate good sperms to keep it going. I do not know how it is in India, but that could be happening. Freezing sperms and eggs is an option, but if they have been damaged from in-utero exposure earlier, they are not going to be very good for conception.
Swan is professor of environmental medicine and public health, Icahn School of Medicine at Mount Sinai, New York City
Count down: How Our Modern World is Threatening Sperm Counts, Altering Male and Female Reproductive Development, and Imperiling the Future of the Human Race
Author: Shanna H. Swan with Stacey Colino