Fireworks are a key part of a wide number of public celebrations around the world, including Australia Day (January 26), the Festival of Sant Joan in Genoa, Italy (June 24), US Independence Day (July 4), Bastille Day (July 14), National Day in Signapore (August 9), Diwali in India (October-November), Guy Fawkes Night in the United Kingdom (November 5) and New Year’s Eve in Jakarta, Indonesia (December 31). But while they are a visual delight, fireworks are anything but innocuous. Research has shown that they can cause significant air pollution and the residues they leave behind – including strontium, barium, cobalt and lead – can be highly dangerous.
A less-known fact is that fireworks contain significant amounts of perchlorate, a chemical of particular concern because of its potential effects on foetal brain development. A 2014 study published in Journal of Clinical Endocrinology & Metabolism examined data from more than 21,000 pregnant women in the United Kingdom and Italy. All of tested positive for perchlorate, and many also had low iodine levels. Children born to women with the highest levels of perchlorate and the lowest levels of iodine were found to be at greater risk of significant IQ loss. So what’s the connection between perchlorate, iodine and IQ?
Perchlorate and thyroids
The answer is that perchlorate blocks iodine uptake by the body’s thyroid glands, reducing their ability to produce sufficient levels of thyroid hormone. This hormone (and hence iodine) is needed for normal brain development. Since the 1970s most children world-wide are tested at birth to ensure they have enough thyroid hormone. If not they are given thyroid supplementation. Thyroid hormone is needed before birth as well, and it was recently demonstrated that a pregnant women’s thyroid hormone levels are vital for her child’s future IQ and brain structure.
As a consequence, too much perchlorate or other factors that interfere with thyroid function are bad news for pregnant women. In the United States, the Environment Protection Agency has estimated that up to 16 million people could be drinking perchlorate-contaminated water. Worse, because perchlorate is highly soluble in water as well as colourless, tasteless and odourless, people won’t know if their water is safe without it tested.
Perchlorate is thus a problem for human health because it interferes with production of thyroid hormone, something we all need. The condition of not having enough is called hypothyroidism, and can cause us to become tired, depressed and overweight. So essential is thyroid hormone that some doctors have referred to it as the “fire of life”.
The importance of thyroid hormone for pregnant women and young children cannot be understated: The lack of either iodine or thyroid hormone during early development, especially the foetal and perinatal periods, results in lower IQ as well as an increased risk of neurodevelopmental disease such as autism spectrum disorder or attention deficit hyperactivity disorders. It has been estimated that neurodevelopmental disorders affect 1 in 6 American children today. In the United Kingdom, it is estimated that 1 in 100 children are diagnosed with autism spectrum disorder, while in the US the rate is approximately 1 in 68. There was an unprecedented and worrying increase in autism spectrum disorder incidence between 2000 and 2014, and given that human DNA has been relatively stable over that time period, genetics are unlikely to explain this increase.
An increasing number of scientists and health professionals, including paediatricians and psychiatrists, are focusing on the multitude of chemicals to which we are exposed on a daily basis that can affect brain development. Of particular concern are chemicals that disrupt hormones – endocrine-disrupting chemicals as they are called. When thinking of brain development and neurodevelopmental disorders, experts immediately think of the main hormone needed for brain development: thyroid hormone. Hence the concern over perchlorate, which is notorious for interfering with our bodies’ capacity to make this hormone.
Fireworks are by no means the only source of perchlorate in our environment. Because it’s highly soluble in water and stable, perchlorate can contaminate croplands and be taken up by vegetables and fruits grown there. Foods with the highest documented levels of perchlorate include melons, dairy and leafy vegetables such as spinach and lettuce. Given the vulnerability of the rapidly growing brains of babies, another particularly unfortunate source is breast milk and infant formula.
New-borns are particular vulnerable, not only because their brains are growing quickly, but they also absorb more food and water for their body weight. But both cows-milk and soy-based infant formulas have been found to contain significant levels of perchlorate as well. Yet soy products are not at option, as they contain yet another compound that interferes with thyroid hormone production, genistein. So, soy-fed infants and children are doubly at risk.
In the United States, perchlorate can even be used in food packaging. Despite well-founded objections from a number of NGOs, the US Food and Drug Administration recently upheld their 2005 decision to allow perchlorate to be used as an anti-static or sealing agent.
Ironically, the same administration reported that levels of perchlorate in the American diet had increased significantly since this decision was taken. Comparing results from two surveys made between 2003-2006 and 2008-2012, revealed significant increases in perchlorate content in various foods, with packaged foods such as salami showing increases of 150-fold. Certain samples of infant food also showed an increase of more than 100-fold. Overall it was estimated that the perchlorate content of the food eaten by infants and toddlers had increased by 34 and 23 % since the FDA decision.
In Europe, perchlorate can also be found on food, as indicated in a 2017 study, “Dietary exposure assessment to perchlorate in the European population”. In toddlers and children – the most vulnerable populations along with pregnant and nursing women – maximum levels were ten times as high as in adults. Food is thus a significant source of perchlorate both sides of the Atlantic.
Finally, perchlorate is not the only chemical that affects thyroid hormone production. Others include pesticides, per-fluorinated compounds, flame retardants and plasticisers. Because multiple thyroid-hormone disrupting chemicals are found in human amniotic fluid, babies are exposed during their entire development in their mother’s womb. My team recomposed a mixture of chemicals commonly found in human amniotic fluid, including perchlorate. They were used at exactly the same concentrations in amniotic fluid as measured by epidemiological studies, and we found that the mixture affected not only thyroid hormone signalling but also brain development, brain gene expression, numbers of neurons in the brain and behaviour.
So what can be done?
What can be done if governmental agencies continue to fail to regulate perchlorate and other thyroid disrupting chemicals? First, try to limit the effects of perchlorate:
- If you’re pregnant or nursing, use iodised salt. Studies show that women increase the iodine content of their breast milk when using iodized salt.
- Take vitamin and mineral supplements that contain 150µg iodine per tablet per day, especially if pregnant or breast feeding. This meets half of the WHO recommendations for iodine intake in pregnancy; the remaining half will come from a balanced diet.
- Eat as much fresh, preferably organically grown, produce as possible. Organically grown produce will have lower pesticide levels. Certain pesticides can act as thyroid disruptors at high levels.
- Reduced the use of packaged foods. In addition to perchlorate, packaging can contaminate food with other thyroid disruptors, such as phthalates.
And, of course, skip the fireworks displays. They may be beautiful, but the consequences of perchlorate exposure for you and your infant’s health could be serious.
Barbara Demeneix, Professor Physiology/ Endocrinology, Muséum national d’histoire naturelle – Sorbonne Universités.
This article first appeared on The Conversation.