Updated | Fireworks chemicals found in tap water

The amount of perchlorate found in tap water is on the low side but when combined with the higher amounts found in other sources like dust and food grown on contaminated soil, it could pose a danger to children’s health

Perchlorate from fireworks is contaminating Malta's water source, giving rise to potential adverse health affects (File Photo)
Perchlorate from fireworks is contaminating Malta's water source, giving rise to potential adverse health affects (File Photo)

Exposure to fireworks is so pervasive in Malta that perchlorate – the chemical used in fireworks production – is contaminating Malta’s water sources, according to a study by chemistry lecturer Colette Pace and University of Malta rector Alfred Vella.

Although the amount of perchlorate found in tap water is on the low side, when combined with the higher amounts found in other sources like dust and food grown on contaminated soil, it could pose a danger to children’s health.

“If all of the sources are taken into consideration (food, water and exposure to dust – inhaled and ingested), the amount of perchlorate ingested will be higher than the minimum exposure limit which causes adverse effects in children,” Colette Pace told MaltaToday.

In a subsequent reaction, the Water Services Corporation said that tests it carried out in 2017 found traces of perchlorate in ground water that were 50 times lower than the limits recommended by the World Health Organisation. The limits traced in tap water were even lower, posing no danger to human health, the WSC said.

Perchlorate has never been analysed in water samples locally. The previous studies published were all for dust samples.

“From the results it is clear that most of the water samples (tap water) contained perchlorate at low concentrations while higher concentrations were detected in surface run-off water, collected after the first rain after the summer months, during which there is a high incidence of pyro-technic activity,” Pace told MaltaToday.

Perchlorate can interfere with the human body’s ability to absorb iodine into the thyroid gland, which is a critical element in the production of thyroid hormones.

In adults, thyroid plays an important role in metabolism, making and storing hormones that help regulate the heart rate, blood pressure, body temperature, and the rate at which food is converted into energy. In foetuses and infants, thyroid hormones are critical for normal growth and development of the central nervous system.

Pace said the concentrations in water were low, compared to those found in dust samples which emerged from research conducted by herself and Vella in previous years.

“The reason is because the perchlorate is diluted in the aquifers, since it is very water soluble. However, perchlorate is very stable, so it is a very persistent pollutant.”

Pace said the only source of perchlorate locally is fireworks, resulting in a high concentration in dust, which may settle via dry deposition or wet deposition (rainfall).

The study found that the concentration in some drinking water supplies analysed in the study was close to, and in some cases, higher than the recommended limits on the presence of perchlorate mandated within the state of Massachusetts in the USA.

The EU has, so far, issued no guideline values on the amount of perchlorate in water.

Perchlorate detected in tap water

Between 42% and 89% of tap water samples analysed in three sampling campaigns between 2012 and 2013 contained perchlorate above detection limit and had mean concentrations ranging from 0.4 to 1.6 μg L-1, suggesting contamination levels similar to those reported from China but lower than levels reported from the USA.

The state of Massachusetts recommends a 2 μg L-1 limit while California has promulgated a standard of 6 μg L-1.

“The quality of Malta’s limited freshwater resources appears to be affected by contamination resulting from the only known source of perchlorate, namely the burning of fireworks,” the study concludes.

How perchlorate reaches the water supply

Chemicals in pyro-technic devises are not entirely consumed in the explosions and the post-explosion debris containing chemicals is dispersed in the environment by wind and other agents.

Residues from fireworks in airborne dust may either settle on the ground as contaminated dust, or dissolve partly in rainwater to release soluble substances that can reach the water table or the sea as coastal run-off.

Some of this also ends in tap water, which consists of a mixture of ground water and desalinated water.

The Vella-Pace study concludes that perchlorate contamination in Malta’s water sources is probably unique “in that it appears to result from the combination of an intense and prolonged religious festival related to pyro-technic activity coupled with a territory size of limited geographical extent.”

The results of the study

The study ‘Contamination of water resources of a small island state by fireworks-derived perchlorate: A case study from Malta’, was based on samples taken from run-off water, the water table and tap water in 2012 and 2013. The study was published in the international journal Environmental Pollution.

Ground water was collected directly from the aquifer from 18 sites during April and July 2012. Rainwater run-off was collected from six sites during November 2011, September 2012 and August 2013, following the first rainfall after dry season. Tap water was collected from 24 sites during March and September 2012 and March and October 2013.

The highest concentrations, sometimes exceeding 110 μg L-1 were found in run-off water taken after the first storms occurring during the dry summer period during which fireworks activity escalates. 82% of run-off samples collected during August and September contained levels of perchlorate above natural value.

Perchlorate was detected in forty-four per cent of the groundwater samples with a mean value of 1.09 μg L−1. Between 42% to 89% of the tap water from three sampling campaigns contained perchlorate above detection limit.

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