No serious public health risk from quarries

An air quality monitoring programme in Yaldhurst shows no serious public health risk to residents from airborne dust.

  • Results well below the international guideline for Respirable Crystalline Silica dust
  • Tougher enforcement promised
  • Nuisance dust above short-term guideline for periods of time on nine of the 120 monitored days. On those nine days, there were 13 exceedances spanning from one minute to less than one hour.

The results, released today, follow a four-month monitoring programme run by Environment Canterbury, with Canterbury District Health Board and Christchurch City Council also involved.

Environment Canterbury chief operating officer Nadeine Dommisse said in late 2016 some Yaldhurst residents came forward with concerns about the health effects of dust coming from the quarries.

“The joint agencies’ primary concern is the health of the community. We agreed it was important to understand if respirable crystalline silica, a fine dust that can cause serious health problems, was present in airborne dust around the quarries. And, if so, we needed to determine if it is at a level that poses a long-term public health risk to residents.”

“We also wanted to understand how much nuisance dust was in the air, commonly called PM10 due to the size of the dust particles,” she said. “Ultimately, this led to the Yaldhurst Air Quality Monitoring programme.”

Canterbury Medical Officer of Health Dr Ramon Pink reviewed the results.

“Overall, the results show there is no serious public health risk to Yaldhurst residents from airborne dust,” he said. “Nuisance dust levels will not cause long-term health effects, but we know it can cause irritation and symptoms of concern in some people and we have prepared a factsheet with advice for residents.”

Dommisse said “While the results show there is no serious public health risk, there is a nuisance dust issue from time to time.”

“We appreciate nuisance dust is a concern for some residents, and we want them to know we have, and are, taking this seriously.”

“We agree quarry dust management hasn’t been good enough in the past. It is clear more needs to be done by all parties, including the quarry operators themselves to avoid dust nuisance issues,” she said. “Today, we are signalling new tougher quarry dust management and monitoring requirements.”

“We’re going to require all quarries within 500 metres of someone’s home to install dust monitors on their boundaries by December 1.  If there is no practicable reason why these boundary monitors are not in place by December 1, we will be taking enforcement action.”

An example of how these boundary monitors work is that they run continuously and must be fitted with an alarm system to send the quarry manager a message if it starts getting close to the threshold level for nuisance dust.  If the alarm is triggered the quarry will be expected to take whatever action they need to, such as stopping work or adding more water carts, to ensure the dust doesn’t breach the Ministry for the Environment’s 1-hour nuisance dust guideline level.  If the guideline is breached the quarry will need to cease operations until dust levels have been managed to acceptable levels.

Quarry operators would have to make this data available to Environment Canterbury, and inform the regional council if there was a breach.

“If a quarry breaches the trigger level, we’ll investigate to find out what action they took to stop dust leaving the quarry before deciding what further action we need to take.”

The Yaldhurst Air Quality Monitoring programme was run by an independent company, Mote, and was designed with input from residents, the quarrying industry and the agencies involved.  It was peer reviewed by international experts to ensure it was robust and comprehensive.

Read more about quarries in Yaldhurst .

Frequently asked questions
What is PM10?
Particulate matter less than 10 microns in diameter. PM10 is made up of things like smoke from home heating, industry and vehicles, as well as dust and sea salt.
What is Respirable Crystalline Silica (RCS)?
Crystalline silica is a natural substance found in rocks, stone, sand and clay.  Dust containing silica is created when these materials are cut, ground, drilled or otherwise disturbed.  If these dust particles are about 4 microns or smaller then they become known as respirable crystalline silica.  The silica-containing dust particles that can be breathed in are not always visible to the naked eye
How long did you monitor for?
We monitored PM10 from 22/12/2017-21/04/2018 and RCS from 19/01/2018-21/04/2018.  We are still waiting for the final results of the fourth month of RCS monitoring, but decided to release these results now.
Did you monitor for long enough?
Yes – we believe three months data gives us sufficient information.
What did the results show?
The results of the Yaldhurst Air Quality Monitoring programme show no serious public health risk to residents from airborne dust.  The results showed that RCS dust levels are well below the international guideline.  Nuisance dust (PM10) was above the short-term guideline for periods of time on nine of the 120 monitored days. On those nine days, there were 13 exceedances spanning from one minute to less than one hour.
How can we trust the results of the monitoring programme?
The programme was designed and implemented by an independent company, Mote, who are experts in the field of dust monitoring with a proven record in this type of work and it was peer reviewed by a specialist from the Queensland government.  Its design also had input from residents, the quarrying industry and the agencies involved.  After Mote finished its design, it was sent for another independent peer review to ensure it was scientifically robust.
We understand some of the monitors were tampered with. What does this mean for the results?
There was one RCS monitor at Site 1 that was tampered with, which did not have a camera on it as the landowner had not given permission.  Due to this tampering, we stopped and put a new filter in.  We’ve continued an additional month of monitoring at this site to do the full three months, however we decided it was important to release the information we have now, rather than wait for another month.
According to the report, we had more rainfall this Summer. What does this mean for the results?
The rainfall was consistent with last Summer in terms of the number of days (33) it rained, however, this Summer had higher amounts on those days it rained.  Canterbury District Health Board are comfortable the results give them enough information to reassure residents that there are no serious long-term public health risk from respirable crystalline silica.  Environment Canterbury agree there’s enough information to show there is a nuisance dust issue from time to time.
Is PM10 dust from the quarries the same as PM10 dust from smoky chimneys?
The make-up of PM10 from quarries and smoky chimneys is different in both size (although both are smaller than 10 microns) and what’s in them (composition).  For example, smoke particles are much smaller than quarry dust so can go deeper into people’s lungs if breathed in, and are generally more toxic than quarry dust.
What guidelines did you use?
All agencies agreed to the guidelines ahead of the monitoring starting.
  • RCS: we used the Californian Chronic Reference Exposure Levels (REL) for RCS. This guideline level is 3 μg/m3 as an annual average.  A chronic REL is an airborne level of a chemical at or below which no adverse health effects are anticipated in individuals indefinitely exposed to that level (California Environmental Protection Agency).
  • PM10: The Ministry for the Environment hourly guideline for nuisance effects is 150 μg/m3, and the 24-hour health guideline is 50 μg/m3.
How long have the quarries been operating in Yaldhurst?
About 40 years.
What should I do if I think dust from the quarries is affecting my family’s health?
If you or your family have a health concern, you should contact your local GP.
Are there any public health concerns for residents right now?
No.  The Canterbury District Health Board has reviewed the results and has no serious public health concerns based on them.
Can dust on its own – without silica particles – cause respiratory symptoms?
Health effects from dust depend on the size of the particles, the amount of dust there is, the composition of the dust, how long people have been exposed to dust, and people’s health. 
The most common symptoms experienced during a period of high dust exposure are irritation to the eyes, ears, nose, throat and upper airways.  Small or fine particles (i.e. particles less than 10 μm), can get deeper into the respiratory tract and lungs and may cause breathing-related problems.  So yes, you can get respiratory symptoms from dust without silica.
What is Canterbury District Health Board’s advice if residents are concerned about dust?
Reducing your exposure to dust is a good idea and may help to reduce health-related issues. When you are irritated by dust, or on poor air quality days, consider:
  • Reducing outdoor activity.
  • Reducing vigorous exercise, especially if you have asthma or a breathing-related condition.
  • Staying indoors in air-conditioned premises if possible and ensure regular maintenance of air conditioner filters and close windows and doors.
  • Vacuuming indoors regularly with a high efficiency particulate air filter.
Does dust affect everyone in the same way?
It is possible that your symptoms have another cause or some people may experience more severe irritations when exposed to dust. This includes:
  • infants and young children;
  • the elderly;
  • people with respiratory conditions, such as asthma, bronchitis and emphysema;
  • people with heart disease; and,
  • smokers.
Is quarrying affecting water quality?
We have not found any contaminants in groundwater with potential health-based effects that can be directly related to the quarrying activities.  This is based on several years of consent monitoring results and a sampling investigation by Environment Canterbury’s groundwater scientists in 2015/2016.
Most of the effects are localised to within the quarry sites themselves.  The magnitude of the effects decreases with distance from the sites, but dissolved concentrations of some soluble ions (such as hardness, chloride, sulphate) may still be above background levels within about a kilometre downgradient.
Will Christchurch City Council/Environment Canterbury issue any further resource consents to quarry operators?
The two councils are required to process an application under the Resource Management Act once lodged and complete.  There is no legal mechanism for the councils to refuse to process an application unless the activity is listed as a prohibited activity in the District Plan or Regional Plan.
What setback distances apply to quarry activities under the District Plan?
The setback distances that apply to quarrying activities depend on the land-use zone where the quarry is located and the type of quarrying activity. Most of the quarries in the Yaldhurst area are located in the Rural Quarry Zone, where the following setbacks apply:
i. Excavation setback from zone boundary – 10 or 20 metres, depending on screening option.
ii. Excavation setback from site boundary within zone – 6 metres.
iii. Crushing and screening plant setback from zone boundary – 100 metres and below original ground level.
iv. Stockpile setback from zone boundary – 50 metres.
In other rural zones, a 250-metre setback is required from a residential- or school-zone boundary (but not from other rural-zone properties).  Otherwise, there is no specific setback in the District Plan, requiring a site-specific assessment of the adverse impacts.
Will Christchurch City Council change the District Plan so that it includes a minimum setback distance between a quarry’s boundary and a residential property’s boundary?
Under the Regeneration Act, Christchurch City Council is currently prevented from changing its District Plan.  This restriction is in place until 2021.
Christchurch City Council, Selwyn District Council, the Canterbury District Health Board and Environment Canterbury have jointly written a letter to the Ministry for the Environment asking them to consider the issue of separation distances between residential properties and quarries given the lack of New Zealand-specific guidelines.
The councils and health board agreed this would increase certainty and provide consistency across the country for regional councils and territorial authorities in land-use planning and managing resource consents.