Delhi Air Pollution: Delhi has been grappling with severe air pollution since early November this year. The Air Quality Index (AQI) of Delhi NCR as of 6:00 pm IST on November 9, 2023 was 771. This air pollution level is considered hazardous. This is the AQI determined based on PM10 levels. According to the US Environmental Protection Agency (EPA), PM10 refers to inhalable particles, with diameters 10 micrometres or smaller.
The AQI of PM2.5 was 541. PM2.5 refers to fine, inhalable particles, with diameters 2.5 micrometres and smaller. PM10 is the primary air pollutant.
According to the World Air Quality Index Project, AQI levels above 300 are considered hazardous. There are severe health implications, for everyone may experience adverse impacts. Since PM2.5 levels are also above 300, people should avoid all outdoor exertion.
A confusion that may arise in the minds of some people is why PM2.5 is not considered PM10 for having a diameter less than 2.5 metres also means having a diameter less than 10 micrometres. The reason why there are different demarcations is that the converted AQI value for PM2.5 can be higher. An AQI of 50 for PM2.5 corresponds to 15.5 milligrams per cubic metre, while an AQI of 50 for PM10 corresponds to 55 milligrams per cubic metre for PM10. This means that more PM10 particles are required to result in an AQI of 50 than PM2.5 particles.
Also, if one compares a concentration of 55 milligrams per cubic metre for PM10 with the same concentration for PM2.5, the resulting AQI for PM2.5 will be higher.
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How air pollution impacts reproductive health
Air pollution adversely impacts reproductive health. Exposure to environmental air pollutants affects reproductive functions, and results in adverse impacts on pregnancy outcomes, fertility, and foetal health. According to a 2010 study published in the Journal of Toxicology and Environmental Health, exposure to ambient levels of air pollutants are linked with low birth weight, intrauterine growth retardation, prematurity, neonatal death, and decreased fertility, both in males and females.
According to a 2017 study published in the journal Environmental Health, air pollutants can affect reproduction as endocrine disruptors, reactive oxygen species inducers, or epigenetic modifications (genetic changes in which the DNA is not permanently damaged).
Effect of air pollution on fertility, and possible pregnancy outcomes
Air pollutants cause defects during gametogenesis (creation of sperms or eggs), resulting in a decline in reproductive capacities in exposed populations.
A 2018 study published in the journal Reproductive Biology and Endocrinology that analysed the effect of air pollution on female fertility said that some of the adverse impacts of air pollution on female fertility were first trimester miscarriage, infertility, and stillbirths.
In people born through vitro fertilisation (IVF) procedures, nitrogen dioxide and ozone were associated with a reduced live birth rate, and PM10 was linked with increased miscarriage.
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Reduced fecundability (probability of a woman conceiving within a specific period of time, especially during the menstrual cycle) was an adverse impact of PM2.5, and particulate matter with diameters between 2.5 and 10 micrometres. The study said that carbon monoxide, nitrogen dioxide, and sulphur dioxide may promote miscarriages and stillbirths.
Air pollution results in fertility difficulties and pregnancy loss. Exposure to particulate matter also increases the risk of infertility
According to the Harvard TH Chan School of Public Health, a June 2018 study conducted by a research fellow at the institute found that women undergoing in vitro fertilisation who lived close to major roadways had a lower chance of a successful embryo implantation and live birth compared to those who lived farther from major roadways and heavy traffic pollution.
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If the proximity of one’s residence to the main road is less than 200 metres, then the chances of air pollution increasing the risk of infertility are high.
“Diesel exhaust particles contain substances associated with anti-oestrogenic and antiandrogenic activities and can affect gonadal steroidogenesis and gametogenesis,” Dr Manju Khemani, Senior Director, Obstetrics & Gynaecology, & Head of Unit, Max Smart Super Speciality Hospital, Saket, told ABP Live.
Antiandrogens are testosterone blockers, and anti-oestrogens are oestrogen blockers. Gonadal steroidogenesis refers to the steroid hormones produced by the gonads. Substances present in diesel exhaust can affect the production of gonadal steroid hormones.
Dr Khemani explained that four possible ways in which exposure to air pollutants impacts fertility are hormonal changes due to endocrine disruption, oxidative stress induced by free radicals, cell DNA alterations, and epigenetic modifications.
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Since both male and female gametogenesis are affected due to air pollution, birth rates decrease.
According to Dr Khemani, the ability of females to conceive may decrease not only due to impacts the number of gametes produced, but also because particulate matter affects gametogenesis on a genetic and epigenetic level (heritable changes associated with altered gene expressions, but not with changes in the DNA sequence).
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Air pollution impact on sperm quality and count
Over the past few decades, a decline in sperm quality has been observed in industrialised countries, said Dr Khemani. Occupational hazards have contributed to this.
“Toll collectors who work on expressways frequently develop sperm abnormalities. Such men have been found to have decreased sperm counts, sperm mobility, and poor sperm morphology,” said Dr Khemani.
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How air pollution impacts the menstrual cycle
Air pollution can also impact menstrual cycle characteristics and the quality of oocytes. According to a 2017 study published in the International Journal of Environment Research and Public Health, fossil fuel consumption can result in the shortening of the luteal phase of the menstrual cycle. The luteal phase, which is the second phase of the menstrual cycle, begins on the 15th day of the 28-day cycle, and ends when the woman gets her period. During the luteal phase, the uterine lining thickens in order to prepare the uterus for a possible pregnancy.
According to the Boston University Medical Campus, air pollution is linked with slightly increased chances of menstrual irregularity and a longer time to achieve regularity in early adulthood.
Since the menstrual cycle is responsive to hormonal regulation, particulate matter air pollution disrupts hormonal activity, impacting the regularity of menstruation.
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A 2006 study published in the International Archives of Occupational and Environmental Health, and conducted by Tomei et al. compared the impact of air pollutant exposure on female police officers performing traffic control in Rome to a control group of female officers performing administrative and bureaucratic activities indoors.
Citing the study, Dr Khemani said that the average level of estradiol was significantly lower in the exposed group during the follicular phase and the luteal phase of the menstrual cycle, but not during the ovulatory phase. No difference between the two groups in terms of disruption of the menstrual cycle was observed.
Estradiol is a hormone produced by the ovaries, and regulates the menstrual cycle. It is the most abundant and potent oestrogen during a woman’s reproductive years, according to the US National Institutes of Health (NIH).
The follicular phase of the menstrual cycle is the one in which the ovarian follicles nature so that one of them releases an egg during ovulation. It is the longest phase of the menstrual cycle. The first 14 days of the menstrual cycle constitute the follicular phase.
The ovulatory phase is the one in which an egg or ovum is released from one of the ovaries. The ovulatory phase occurs on the 14th day of the menstrual cycle.
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How air pollution affects the foetus
Air pollution impacts pregnant women and their developing babies because airborne contaminants can traverse the placenta.
This endangers both the mother and the baby, Dr Nisha Bhatnagar, Medical Director, Infinite Fertility, a specialised egg freezing facility in Vasant Vihar, New Delhi, told ABP Live. “A pregnant woman’s exposure to every 10-microgram per cubic metre increase in PM2.5 could result in a four-gram decline in the baby’s birth-weight, according to a 2018 study conducted in Chennai and its surrounding districts involving 1,285 pregnant women. This exposure during pregnancy may lead to adverse consequences such as preterm labour, stillbirth, low birth weight, and respiratory problems. Moreover, it poses health risks for the expectant parent.The pollutants interfere with the delicate process of lung development in the foetus. Hence, mitigating air pollution is essential to safeguard the well-being of pregnant women and the healthy growth of their babies. Science underscores the pressing need for cleaner air to ensure safer pregnancies.”
Effect of indoor air pollution on male and female reproductive health
Indoor air pollution also impacts reproductive health because indoor pollutants such as volatile organic compounds, formaldehyde, and particulate matter result in hormonal disruptions and oxidative stress. Both male and female fertility can be affected.
Of the 20 most polluted cities in the world, 15 are a part of India. Of all the premature deaths linked to air pollution, 91 per cent occurred in low- and middle-income countries.
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“Indians breathe some of the world’s most toxic air and the country is home to 15 of the 20 most polluted cities in the world, according to a study released in March 2019 by the NGO Greenpeace. By breathing clean air alone, Indians would live 1.7 years longer, on average, according to a December 2018 study led by the Indian Council of Medical Research (ICMR). Around 91 per cent of premature deaths linked to air pollution have been in low- and middle-income countries, according to the World Health Organization (WHO). Just by ensuring cleaner air, countries can reduce their burden of stroke, heart disease, lung cancer, and respiratory diseases,” said Dr Bhatnagar.
Similar to outdoor air pollutants, indoor air pollutants can degrade the quality of sperm and eggs. Egg freezing is a practice that can help preserve the quality of eggs, Dr Bhatnagar suggested.
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