What are PAHs?

PAH is the collective term for a group of several hundred different individual substances that present with multiple, tightly adjoining benzene rings (cores) in their chemical structure. Those in the trade call it Polycyclic Aromatic Hydrocarbons for this reason, or simple PAHs. Typical PAHs include naphthalene (a former moth-proofing agent), phenanthrene, anthracene, pyrene, and benzo(a)pyrene.

Two- to four-ring PAHs with boiling points up to about 400 °C are volatile and evaporate over time; in contrast, four- to six-ring PAHs with boiling points up to 550 °C have low volatility and are almost always bound to dust particles. The most well-known representation of the PAH group is benzo(a)pyrene (BAP), which frequently acts as a lead substance in analytical assessment and toxicological evaluation of contaminated samples.

PAHs always form when organic material is heated or burned under conditions of insufficient oxygen. As a result, they do not just form during the production of coke, but also during combustion processes of all kinds, such as in combustion engines, in stoves and furnaces, when candles soot, when grilling meat and sausage products, when smoking tobacco products, and similar situations. PAHs are therefore virtually ubiquitous in higher or lower concentration and in various compositions. 

Because many PAHs have proven to carcinogenic and genotoxic as well as harmful to the immune system, exposure to them should be kept to a minimum. It is for this reason that the new owners of former US residences were hardly enthused when, along with other chemical remains, higher concentrations of PAHs were also found in the house dust of their homes. If these homes are to be first renovated and then resold, these old remains pose a significant technical, and not least psychological, problem. There are sure to be few who will feel comfortable being forcibly exposed to such hazardous substances. 

It’s difficult to get a truly reliable estimate of the actual danger in this, because people and families have clearly been living in these residences for decades without a problem. Today we go by the prevention principle, and address the questions of appropriate and effective counter-measures.

Measures against PAHs

UZIN does not respond to the uncertainty and perplexity involved in PAH concerns with fear-mongering and overblown claims, but rather with technically thought out, feasible, and affordable decontamination measures that can be relied on to prevent future exposure to PAHs. 

The PAH situation in the affected homes may look quite different depending on location and condition. When making the decision to take decontaminating measures or not, the press release from the Federal Environment Agency of 29/04/1998 will help. After that, the actions required depend on the benzo(a)pyrene (BAP) report as follows (simplified version): 

• Case 1:

BAP in old adhesive (mg/kg): < 10
BAP in house dust (mg/kg): No measurement necessary
Action: none

• Case 2:

BAP in old adhesive (mg/kg): No measurement necessary
BAP in house dust (mg/kg): < 10
Action: situational/medium-term

• Case 3:

BAP in old adhesive (mg/kg): > 10
BAP in house dust (mg/kg): > 10
Action: short-term

Due to the long amount of time lapsed since the homes were built, volatile PAHs have largely disappeared from the adhesive layer. Thus PAH vapours in the indoor air should only be expected in the rarest cases. Today, PAHs can mainly be detected as deposit build-up and components of house dust in affected homes. This dust pollution can be explained by the emergence of PAH-contaminated adhesive particles from ever-present joints and cracks in the flooring and along the walls. 

This means that the affected homes can only be effectively  decontaminated with methods that prevent any further formation or release of PAH-contaminated dusts. In addition, any action should conform to the technical rules of flooring engineering and be feasible with standard technical means. Acceptance of a decontamination method depends on an assessment of economical, technical, and ecological aspects, and is ultimately based on the cost-effectiveness of the measure. 

This holistic formula for consideration is the basis of the current UZIN PAK decontamination system with the three following options for procedure:

• UZIN containment method: Fixed old wood flooring remains in place
• UZIN sealing method: Old wood flooring is removed, old adhesive is sealed
• UZIN removal method: Old wood flooring and old adhesive are removed

Depending on the situation at hand construction of a new floor covering takes place on either the old wood flooring left in place, after removing the old wood flooring on the varnished old adhesive, or on the screed, from which all old layers have been completely removed. In the event that the old screed has also been removed, there is no need for special decontamination, because then the work can be done on the new screed that’s brought in anyway, according to recognised rules of the trade. 

When using the UZIN PAH decontamination system, keep in mind that types of floor covering other than wood flooring are eligible, including textile or resilient floor coverings, linoleum, and ceramic.
There are set-up schematics and job instructions for different types of new floor covering for each of the three UZIN decontamination processes.