06 Apr 2024 Bottled water: microplastics and nanoplastics
John Weaver, Chairman of the South African National Bottled Water Association (SANBWA) adds some perspective to the noise that’s resounding around the issues of micro- and nano plastics….
Microplastics are 1 µm to 5 mm in length and nanoplastics are smaller than 1 μm. Collectively referred to as mnps, these mnps are omnipresent and ubiquitous in our daily lives. So much so that there is zero chance of any human avoiding either inhaling or ingesting mnps – even if they excluded any contact with plastics in their day-to-day lives.
The sources and estimated quantities of these mnps, as referenced here, are:
- textiles and clothing 50‑75%
- vehicle tyres 10-20%
- city dust 10-20%
- road markings 3‑5%
- and personal care products 1‑3%.
These mnps will end up in our rivers and ultimately our oceans, either via rainfall runoff or by wastewater that discharges in our rivers. For example, wastewater from the washing of clothes carries very high levels of mnps.
A major concern is the effect of mnps on human health. And this has led to several alarmist newspaper headlines whenever new research is released. To date, however, there is little to no evidence of direct impacts of mnps on human health.
The WHO recently released a very comprehensive and wide-ranging study of all available research and the conclusion is “The weight of the scientific evidence provided by current data on adverse effects of mnps on human health is low.” (WHO 2022).
A disproportionate number of research projects into mnps have involved water, either drinking water, municipal supply water or bottled water. The reason for the concentration or focus on water is because water is clear, and separating the mnps from the water is usually simple filtration. Consider how much more difficult it would be to analyse for mnps in hamburgers or potato chips.
As such bottled water is a relatively simple research subject.
After reviewing the numerous bottled water research projects, I have three observations to make:
- Broadly speaking there are two types of bottled water. Mineral water (aka spring water) is water derived directly from underground sources (groundwater), whereas prepared water is mostly surface water that is filtered and sterilised and bottled.
- Groundwater sampled directly from the borehole usually has very low (below the Limit of Detection) numbers of mnps per litre. This is due to the Earth acting as a thick filter system when rain carrying mnps infiltrates down to the water-table. When these waters are bottled, the numbers remain low through the bottling process, until capping. However, the process of capping releases detectable amounts of mnps. This is ascribed to abrasion of the plastic caps during the capping process (Weisser et al 2021)
- Surface water has very high levels of mnps. This due to rain falling on our streets and running off into our rivers, and also due to waste-water discharge. If the bottled water is sourced from surface water, then high levels of mnps are detected. The method of preparation will play a role. If the water is filtered using membranes and activated charcoal, followed by ozonation the levels will be high. Reverse osmosis (RO) however will filter out much of the mnps. But in turn, if the filter material is plastic based, then mnps will be added. (Weisser et al, 2021: From the Well to the Bottle: Identifying Sources of Microplastics in Mineral Water. )
In conclusion, as bottled water is a simple target for analysis compared to the hundreds of other sources of ingestion of mnps, it would be unfair to single out bottled water alone.