My Account
By Ralph Cooney
In the dry late summer months, driving along unsealed country roads usually involves clouds of fine dust from the car in front coating one’s car and creation of more dust for any car following. For most of us, this seems to be a tolerable price of living in beautiful but isolated locations. About 40 per cent of the NZ road network in 2020 was unsealed roads (Institute of Public Works Engineering Australasia, IPWEA, 2020). Public discussions about country roads usually centre around the cost of resurfacing and, hence, often lead to anxiety about rate increases.
Historically, road dust has been considered just a nuisance. However, recently there is another important dimension to this matter that is attracting more attention in New Zealand and overseas: the health impacts for travellers and residents of inhaling road dust.
The Ministry of Health has published a 2019 report ‘Health Impacts of PM10 from Unsealed Roads in Northland’. PM10 refers to dust particles less than 10 micrometers in dimension. These very small particles are more dangerous because they can penetrate the human respiratory system more effectively than larger dust particles.
PM10 dust particles are roughly the diameter of the very finest wool fibres and are 10 times smaller than the smallest thing a human eye can see. The monitoring data recorded as part of this report recorded 27 instances of exceeding the 24-hour national environmental standard. One exceedance is permitted within any 12-month period.
The 2019 Ministry of Health assessment showed an estimated 0.6 cases of premature mortality per year or six cases of premature mortality over 10 years due to unsealed road dust. The total cost of all adverse effects assessed was between $1.2 and $3.8 million per annum in 2017 dollars.
The US National Institute of Health (NIH) conducted a review of specific health risks across several countries including USA, UK, Italy, Iran and China. This review includes the number of times a particular health issue is mentioned across official reports. The review found 17 studies that reported that exposure to road dust had adverse health effects on the respiratory system. These effects included asthma, as well as forms of respiratory carcinoma such as mesothelioma. This literature review found studies that reported the components of road dust particles (including fine silica, various light and heavy metals and organics) to be associated with multiple health effects, in particular on the respiratory and cardiovascular system.
A methodology was developed by the NZ Government to help assist road managers to assess and prioritise dust mitigation-related activities. This approach considers risk factors, including the nature, number and speed of vehicles, local weather conditions and topography and also sensitive residential, ecological and horticultural locations.
The conclusions were that firstly, as the NIH review above recommended, there is an urgent need for a more complete risk assessment of the effects of road dust on human health. Secondly, NZ should evaluate new international road surfacing materials. These new sustainable roading materials include recycled plastic pellets in bitumen, pyrolysis bio-bitumen from general waste, solar roadways and so on.
