Hazardous building materials

Pavement sealant: Dangerous and pointless?

Everyone knows that the construction industry is a hazardous one and as such health and safety is a prime concern when dealing with heavy lifting equipment and potentially fatal building materials, however the materials shouldn't have debilitating effects on the public once construction is over.

Over the years, a number of building materials have been replaced with healthier alternatives once their potential for health risk has been discovered - asbestos and lead paint being the prime examples.

However, a commonly used coal-tar-based pavement sealer that is often used in driveways, sideways and car parks has been discovered to contain carcinogenic compounds that can easily be carried into homes.

Carcinogenic sealant

Studies by the the US Geological Survey (USGS) found that the coal-tar pavement sealant, that is typically used on the east side of the country, contains 1000 times more polycyclic aromatic hydrocarbons (PAHs), which are by-products of fuel burning, than its asphalt-based counterpart used throughout the West. This compounds can also be picked up on shoes and tracked indoors, causing a potential cancer risk in homes.

Sampling pavement dust from across the US, the team discovered much higher levels of PAHs in the dust from pavement coated with coal-tar sealant than pavement coated with asphalt-based sealant or no sealant at all. In their report, published in Environmental Science & Technology, Barbara Mahler, a USGS research hydrologist involved in the research, said "We thought that concentrations of PAHs were so high in parking lots that they may be affecting house dust."

The team is now working with the EPA to ban the harmful sealant, but a nationwide ban will still take some time and a phase-out doesn't come easily.

Previous precedents

In the past, the US has phased out building materials that were discovered to put the public at risk. In the 1940s, lumber was treated with a preservative called chromated copper arsenate (CCA) to protect against rot and insect damage. It was discovered that the preservative leaked chromium and arsenic into surrounding soil contaminating surrounding plants.

Seeing as the wood was primarily used in playgrounds, the use of CCA was eventually phased out...but by 2003. It has now been replaced by new water-based preservatives and composites such as recycled plastic lumber.

In this case however, the researchers don't even believe an alternative is needed, believing that sealant doesn't even extend a pavement's life span when used. What is clear however is that constructors need to start phase this product out as soon as possible.

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