Carcinogenic mineral found in US road gravel
MedWire News: Researchers report that an asbestos-like mineral, erionite, is present in cancer-causing quantities in gravel used to surface more than 300 miles of roads in the state of North Dakota in the USA.
Previous investigations have linked exposure to erionite with an abnormally high rate of malignant mesothelioma in several villages in Central Anatolia in Turkey where, as a consequence, preventative measures have been implemented regarding exposure to the mineral.
In this study, published in the journal PNAS, Michele Carbone (University of Hawaii, Honolulu, USA) and colleagues compared the type of erionite found in Turkey with that found in North Dakota, and used erionite exposure levels in the Turkish villages to determine airborne levels of erionite constituting a significant risk for malignant mesothelioma.
Natural erionite deposits are present in 12 US states. Based on the theory that exposure to erionite may have increased in the USA due to increased urban development, the team took roadside air samples from over 300 miles of roads in North Dakota.
The researchers found that airborne concentrations of erionite taken during sampling in North Dakota were similar or higher than those taken in the Turkish villages. For example, stationary roadside air samples taken along a road near a school bus stop in North Dakota contained higher amounts of erionite (0.11 structures/cubic centimeter [s/cc] total transmission electron microscopy [TEM], 0.01 s/cc phase contrast microscopy equivalent [PCME]) than all such samples taken in the Turkish villages.
In addition, air samples taken from personal breathing zones of people working in a road maintenance garage and a social services office in North Dakota during sweeping and housekeeping jobs (0.18 s/cc total TEM and 0.06 s/cc PCME) were similar to those of people working in the villages of Boyali and Karlik in Turkey, which have malignant mesothelioma mortality rates of 6.25% and 7.41%, respectively.
The researchers examined the structure of the erionite samples taken from both locations and found them to be very similar, with identical biological activity.
"Based on the similarity between the erionite from the two sources, there is concern for increased risk of mesothelioma in North Dakota," commented Carbone.
These results are very concerning as malignant mesothelioma acquired as a result of erionite exposure can take 30-60 years to manifest, and many deposits in the USA have only been mined or exposed to the atmosphere in recent years. This suggests that the number of cases of malignant mesothelioma could soon be on the increase, say the authors.
"Our findings provide an opportunity to implement novel preventive and detection programs in the US similar to what we have been doing in Turkey," said Carbone.
By Helen Albert