Over the years, new substances dissolved in water have been discovered — the so-called emerging pollutants — some of which are considered dangerous to health when present in high concentrations. Heavy metals, chemicals and pharmaceuticals that must be monitored and, where necessary, filtered out.
For water to be classified as drinking water, it must meet the chemical and physical requirements set out by law, in particular by legislative decrees 31/2001 and 27/2002, derived from European Directive no. 98/83/CE. The law establishes which substances and bacteria may or may not be dissolved in water intended for human consumption, and above all in what concentrations. Over the years, however, attention has also shifted to what are known as "emerging pollutants" — substances dissolved in water that have only recently been discovered, or substances for which studies and scientific assessments have confirmed their danger to human health.
These are substances or metals that, when present in certain concentrations, can pose risks to health. This is the case with heavy metals, such as arsenic, cadmium, lead and mercury, or the more recently identified Pfas (perfluoroalkyl substances), or allergens such as nickel. There is no shortage of chemical substances either, including herbicides, pharmaceuticals and narcotics.
Nickel, for example, is a naturally occurring metal, but it can cause allergic reactions in some people, both through contact and through ingestion via food or water containing it. In drinking water, it must not exceed 20 micrograms per litre. In 2015, the Efsa established "a safe level, known as the tolerable daily intake (TDI), of 2.8 micrograms per kilogram of body weight", and that "current chronic dietary exposure to nickel is a cause for concern for the general population".
There are also elements that have become hazardous as a result of updates to legal parameters, whereas previously they were not. This is the case with chromium VI (hexavalent), one of the ionic forms in which the metal occurs in nature. The latter, if present in high doses, can be highly toxic. Italian law previously set an overall limit for chromium of 50 micrograms per litre, but Decree 14/2016 established a maximum limit of 10 micrograms per litre for chromium VI, with a mandatory requirement to test for this parameter whenever total chromium exceeds 10 micrograms per litre.
There are also a whole range of substances for which no national legal limit yet exists, but only guidelines issued by the World Health Organisation. These are therefore regulatory gaps, due either to limited knowledge of the health effects of such substances, or to their more recent discovery in surface waters and waters intended for human use. This is the case with the so-called Pfas — a series of chemical substances used in a great many industrial processes for the production of clothing, footwear, utensils and much more.
Following the emergency recorded in Veneto in 2013, the Region decided to drastically lower the limits for Pfas in water, moving from the previous 530 nanograms per litre to the current 90 nanograms per litre, in line with the laws of Sweden (90 ng/l) and the United States (70 ng/l). To date, however, neither a national nor a European law establishing such limits exists.
Today, numerous solutions exist on the market for filtering and eliminating the most problematic substances, which are available and already used both by companies managing integrated water services and by individual citizens. It is important to rely on reputable companies with proven expertise, capable of supplying certified products that conform to the highest quality standards. Among the systems currently available are filtration plants, used primarily to treat water containing suspended substances.
Softening systems are also important, as they are capable of reducing scale build-up, as are activated carbon systems, which lower the levels of pollutants such as herbicides or other organic substances of industrial origin. The final step is the installation of a reverse osmosis system, which makes it possible to retain most dissolved substances, guaranteeing a constant supply of mineral salts and drinking water that is safe and compliant with the law.