The present invention refers to a method for reducing surface contamination by volatile organic compounds, also referred to as VOCs (acronym for“volatile organic compounds”), in particular formaldehyde.

Formaldehyde (also called formic aldehyde or methanal) is the simplest of the aldehydes. Its chemical formula is CH2O, and its CAS number is 50-00-0. In a 37% aqueous solution, it is also commercially known as formalin or formol.

It is well-known that formaldehyde is a powerful bactericide. For this reason, in aqueous solution, it is widely used as a disinfectant for domestic use and is also used as a bactericide in the production of fabrics at the industrial level.

Formaldehyde solutions are also used to store samples of biological material, as well as in embalming techniques.

Formaldehyde is also used in aqueous solution (a form in which it takes the name“formalin”) for the production of vaccines, both to produce anatoxins (or toxoids), i.e. toxins that lose their toxicity but maintain their immunogenicity, from bacterial toxins, and to produce vaccines based on killed microorganisms.

Most of the formaldehyde produced, however, is intended for the production of polymers and other chemical compounds. Formaldehyde, following the reaction with phenol, polymerizes producing Bakelite, a thermosetting resin. Similarly, formaldehyde reacts with urea and melamine, the resins of which are used as plastic laminates, adhesives and insulating foams.

Formaldehyde is also a reagent used to produce other organic compounds, many of which are polyols, such as pentaerythritol. Formaldehyde is identified by the code E 240 as a food additive, in particular as a preservative. Actually, formaldehyde is present in wood smoke and is, together with polyphenols, responsible for the preservation of smoked food products.

Formaldehyde, together with urea, is also used as an adhesive varnish for wood chipboard panels, melamine panels or medium-density fiberboard (MDF) panels. It is further contained in the sound-absorbing panels of false ceilings and in the partition walls of open-plan offices in which, over the years, it tends to volatilize into the surrounding environment.

This substance is also used for the production of isoprenol. In textile dyeing, it is used in the application with naphthols to give greater stability to naphtholic solutions and in the subsequent treatment of some tinctures obtained with direct dyes in order to improve their fastness to water and to washing in general.

Given the widespread use of resins derived from formaldehyde in the production of manufactured products, insulating coatings and foams, which tend to release formaldehyde molecules into the environment over time, the latter is one of the most widespread indoor pollutants. At concentrations in the air above 0.1 ppm, formaldehyde may irritate the mucosae and the eyes by inhalation. Ingestion or exposure to consistent quantities of formaldehyde are potentially lethal: in particular, its carcinogenicity has been found in rodents, where it causes a higher than normal incidence rate of nose and throat cancer. Formaldehyde is able to interfere with the bonds between DNA and proteins.

Since 2004, the International Association for Research on Cancer (IARC) has included formaldehyde in the list of substances definitely considered to be carcinogenic to the human species. Even if the concentrations of formaldehyde normally present inside buildings are generally low and therefore not particularly worrying, the risks to workers in industry using formaldehyde must be carefully assessed.

The World Health Organization has indicated 100 pg/m ³ (equal to 0.1 parts per million - ppm) as the maximum acceptable concentration limit for formaldehyde in the home. Since January 1, 2016, formaldehyde has moved from the classification of “suspected to cause cancer” to“may cause cancer” (Regulation (EU) No. 605/2014).

There is therefore the need to provide a method to reduce concentrations of volatile organic compounds that are highly dangerous to human health when inhaled, in particular formaldehyde. This need is particularly felt with reference to the sanitization of surfaces contaminated with VOC residues, in particular formaldehyde residues.

Such need has now been met by the present invention, which provides a method for sanitizing surfaces contaminated with formaldehyde residues having the characteristics indicated in claim 1 below.

Preferably, the contaminated surfaces that are sanitized by the method of the invention are the surfaces of some objects and instruments that typically come into contact with formaldehyde, such as, but not limited to, laboratory laminar flow hoods and biopsy containers.

The method of the invention allows advantageously for the concentration of formaldehyde on the treated surfaces to be reduced through oxidation by an aqueous chloro-oxidizing solution that is sprayed, nebulized or atomized on the surfaces to be sanitized.

An aqueous chloro-oxidizing solution known per se is anolyte. It is conventionally produced at the anode by electrolysis of a saturated aqueous solution of sodium chloride (NaCl) or potassium chloride (KC1). The solution produced by electrolysis of a saturated aqueous solution of sodium chloride (NaCl) or potassium chloride (KC1) contains active chlorine, predominantly in the form of free available chlorine (hypochlorite ion (ClO ) and hypochlorous acid (HClO)).

The pH of the aqueous anolyte solution is preferably between 4 and 12, e.g. between 4 and 7.5, or between 8 and 12, or between 9 and 11.

The concentration of free chlorine (OC1 , HOC1 and Ch(aq)) in the aqueous anolyte solution is preferably between 150 and 1500 ppm, for example between 150 and 900 ppm, or between 900 and 1200 ppm, or between 500 and 1500 ppm.

Methods for the determination of free chlorine are known in the art, for example the colorimetric method based on the measurement of color intensity developed by the reaction between chlorine and N,N-Diethyl-p-phenylenediamine (DPD) and measurable by means of a spectrophotometer.

In all the embodiments described above, the anolyte solution is stabilized by adding to the solution produced at the anode a stabilizing agent selected from the group consisting of hydrochloric acid (HC1) from 50 to 250 mg/l, sulfuric acid (H2SO4) from 50 to 350 mg/l, phosphoric acid (H3PO4) from 50 to 500 mg/l, periodic acid (HIO4) from 10 to 1000 mg/l, sodium chloride (NaCl) from 1 to 30 g/l, and any combination thereof. Thanks to the present invention, a method for sanitizing surfaces capable of oxidizing formaldehyde vapors has been made available, making the working environment safer, ensuring health security and at the same time being economical and made from natural materials (water and salt). Regardless of the details of the reaction mechanisms, the formaldehyde is decomposed, reacting with the oxidant, so the treatment is more effective.