Urban soils review

Background | Soil tests at childcare facilities | Investigation of other sites | Remediation | Contaminants

Contaminants

The council is employing contaminated land specialists to carry out all the soil testing at the childcare sites.

They test for a range of contaminants, including:

heavy metals such as lead, copper, cadmium, chromium, arsenic, zinc, nickel
mercury
petroleum hydrocarbons
semi-volatile organic compounds
polycyclic aromatic hydrocarbons

Below is a chart detailing the kinds of contaminants that are tested for and the current understanding about health risks.

For the initial assessment of human health risk, Auckland City is currently using New Zealand (Ministry for the Environment) guidelines in conjunction with National Environment Protection Council of Australia guidelines; where threshold values exist for both guidelines, the more conservative value is used. Auckland City is working together with MfE, the Auckland Regional Public Health Service (ARPHS), the Auckland Regional Council and other territorial authorities to address the issue of national standards for human health in urban soil environments, particularly for exposure assumptions relevant to Tier II risk assessments.

Soil testing at childcare facilities has only identified elevated levels of the chemical group known as polycyclic aromatic hydrocarbons (PAHs), lead and arsenic. The council undertakes to investigate any council-owned, residentially-zoned property with significant accessible soil that records levels of benzo(a)pyrene above 0.27 milligrams per kilogram of soil, levels of lead above 300 mg/kg of soil and levels of arsenic above 30 mg/kg of soil.

Contaminants of concern - degree and types of risk

Substance	Description and hazard identification
Lead	What is lead? Lead is found in all parts of our environment. It is a naturally occurring metal and arises from human activities such as the burning of fossil fuels, mining and manufacturing. What is lead used for? Lead is used in the production of batteries, ammunition, and metal products. Lead can be present in fuels, paints, and ceramic products. How can lead affect human health? Lead affects the central nervous system, the kidneys and blood cells. It can lead to hypertension, reproductive toxicity and developmental effects. Lead is classified as a possible human carcinogen, based on animal studies. Exposure to lead can occur through breathing workplace air or dust, eating contaminated food or drinking contaminated water. Exposure may also occur through ingesting lead-based paint chips and ingesting or contacting contaminated soil. What is the degree of risk? The National Environment Protection Council of Australia provides a soil lead limit of 300mg/kg for the protection of human health, for residential use.
Mercury	What is mercury? Mercury is a naturally occurring metal. It exists as metallic mercury, which is the shiny silver liquid found in thermometers, and as mercury salts and organic mercury compounds. A form of mercury (methymercury) can be formed in soil by bacteria. What is mercury used for? Mercury is used in manufacturing, mostly in the production of chlorine gas and caustic soda, and is found in thermometers, dental fillings and batteries. Mercury can enter the environment through the burning of coal and waste. How can mercury affect human health? Mercury affects the nervous system and high levels can permanently damage the brain, kidneys and developing foetus. The inhalation of mercury vapours is particularly harmful. Certain forms of mercury are classified as possible human carcinogens, based on animal studies. Exposure to mercury can occur through breathing in vapours related to dental, health and some chemical industries and vapours from mercury spills and some incinerators. Exposure can also occur through eating shellfish contaminated with methylmercury and ingesting and contacting contaminated soil. What is the degree of risk? The National Environment Protection Council of Australia provides a soil mercury limit of 15mg/kg for the protection of human health, for residential use
Polycyclic Aromatic Hydrocarbons	What are Polycyclic Aromatic Hydrocarbons or PAH? PAHs are a group of chemicals that are formed during the incomplete combustion of substances such as coal, oil, wood and solid waste. Vehicle emissions and tobacco smoke contain PAH's. Mothballs contain a PAH known as napthalene. What are PAHs used for? PAH's are found in coal tar, crude oil, creosote and roofing tar. Some are used in medicines and to manufacture dyes, plastics and pesticides. How can PAHs affect human health? For the purposes of health assessments, PAHs are classified in two groups; carcinogenic PAHs and non-carcinogenic PAHs. Carcinogenic PAHs The PAH benzo(a)pyrene has been shown to cause lung and skin cancer in animals. PAHs in cigarette smoke can cause lung cancer. Reproductive toxicity and damage to lungs, liver, skin and kidneys can occur. Non-carcinogenic PAHs Exposure to large amounts of the PAH napthalene can damage and destroy red blood cells and lead to a form of anaemia. Exposure to PAHs can occur through breathing contaminated air in some workplaces (asphalt and coal-tar plants and solid waste incineration facilities), and air containing cigarette smoke, wood smoke and vehicle exhausts. PAH's can be ingested through eating grilled or charred meats or drinking contaminated water. Exposure can occur through coming in contact with air, water or soil near hazardous waste sites. What is the degree of risk? Auckland City undertakes to investigate council-owned properties which show levels of benzo-a-pyrene equivalence exceeding 0.27 milligrams per kilogram of soil. Tier II risk assessments analysing exposure levels for the most sensitive sub-group (pica children, who are prone to ingest soil) at childcare centres have provided a conservative threshold value of 3.5mg/kg as an internal guideline for assessing potential health risks for this sub-group. This value will vary based on factors such as exposure time and access to food grown on site. Other local authorities and agencies (notably Landcare Research) are currently in the process of deriving their own exposure values. This issue is under discussion with the Auckland Regional Public Health Service and the Ministry for the Environment, in terms of its applicability to the proposed National Environmental Standards for human health in urban soil environments.
Total Petroleum Hydrocarbons	What are Total Petroleum Hydrocarbons or TPH? TPH is a mixture of many different petroleum compounds that originate from crude oil. When testing for these compounds in the environment, it is not practical to test for each compound separately, and the total amount of TPH is therefore measured. What is TPH used for? All petroleum products contain a mixture of TPH compounds and any industry or activity using or producing petroleum products has the potential to discharge TPH into the environment. How can TPH affect human health? Some TPH compounds can affect the central nervous system, causing symptoms such as dizziness and headaches. Others can affect the blood, immune system, lungs, skin and eyes. Everyone is exposed to TPH from sources such as petrol and chemicals used in the home. Exposure can also occur through drinking contaminated water and ingestion, inhalation or skin contact with contaminated soil. What is the degree of risk? The guidelines used for assessing TPH levels in soil are the ministry for the Environment's Guidelines for Assessing and Managing Petroleum Hydrocarbon Contaminated Sites in New Zealand. These provide TPH limits for residential landuse and provide a conservative approach to assessing the risk to human health. Limits are provided for the exposure pathways of inhalation, ingestion and skin contact and for different soil types. For sandy surface soils, the guidelines provide a limit of 500mg/kg for the volatile TPH fraction.
Zinc	What is zinc? Zinc is one of the most common substances in the earth's crust. It is found in air, soil and water and is present in all foods. What is zinc used for? Zinc is used in coatings to prevent rust, in batteries and in metal alloys. Zinc compounds are widely used in industry to make paint, rubber, dyes, wood preservatives and ointments. How can zinc affect human health? Low levels of zinc are essential for good health. Exposures to large amounts of zinc can be harmful and can cause stomach cramps, anaemia, and changes in cholesterol levels. Exposure to high levels of zinc can occur through eating contaminated food, drinking contaminated water and breathing air contaminated by industries such as smelting, galvanising and car repair garages. What is the degree of risk? The National Environment Protection Council of Australia provides a soil zinc limit of 7000mg/kg for the protection of human health, for residential use.
Copper	What is copper? Copper occurs naturally in rocks, soil, water, air and also plants and animals. What is copper used for? Copper can be present in coins, electrical wiring, water pipes and some metal alloys. Copper compounds are used in plant fungicides, for water treatment and as preservatives for wood, leather and fabrics. How can copper affect human health? Low levels of copper are essential for maintaining good health. High levels can cause irritation of the nose, mouth and eyes, and nausea and stomach upsets. Exposure to copper can occur through breathing air, drinking water, eating food and by skin contact with air, soil, water and substances that have high levels of copper. Inhalation or skin contact with copper-containing dust can occur in the copper mining industry and the welding of copper metal. Exposure can occur through the use of some garden products to control plant diseases. What is the degree of risk? Auckland City has adopted an interim value of 370 mg/kg as being conservatively protective of human health.
Chromium	What is chromium? Chromium is a naturally occurring element found in rocks, soil, volcanic dust and gases and animals and plants. The form of chromium known as chromium (III) is the most stable and most chromium in the environment is in this form. What is chromium used for? Metallic chromium is used in making steel. Chromium compounds are used in chrome plating, dyes and pigments, leather tanning and wood preserving. How can chromium affect human health? The possible effects of chromium are dependant on the type of chromium exposed to. No health effects are associated with exposure to chromium (III). Breathing high levels of chromium (VI) can damage the nose while ingesting it can cause stomach ulcers, convulsions, and kidney and liver damage. Chromium is classified as a human carcinogen. Exposure can occur through breathing in contaminated air associated with industries that use chromium. Exposure may also occur through ingesting contaminated food or water. What is the degree of risk? The guidelines recommended by the Ministry for the Environment for the evaluation of chromium levels in soil are the New Zealand Health and Environmental Guidelines for Selected Timber Treatment Chemicals. These guidelines provide a chromium (III) limit of 600mg/kg. This is for residential land use which assumes 50 per cent home-grown produce and is therefore considered conservative.
Arsenic	What is arsenic? Arsenic is a naturally occurring element in the earth's crust and is also found in animals and plants. What is arsenic used for? The primary uses of arsenic are in the preservation of timber and in the manufacture of pesticides. How can arsenic affect human health? Health effects depend on the form of arsenic, with inorganic arsenic compounds more toxic than organic compounds. Breathing high levels of arsenic can irritate the lugs while ingestion can cause death. Inorganic arsenic is classified as a human carcinogen. Exposure can occur through breathing sawdust or smoke from wood treated with arsenic and ingesting contaminated food or water. What is the degree of risk? The guidelines recommended by the Ministry for the Environment for the evaluation of arsenic levels in soil are the New Zealand Health and Environmental Guidelines for Selected Timber Treatment Chemicals. These guidelines provide an arsenic limit of 30mg/kg. This is for residential land use which assumes 50 per cent home-grown produce and is therefore considered conservative.
Nickel	What is nickel? Nickel is an abundant naturally occurring element. It is found in all soil and is emitted from volcanoes. It is found in meteorites. What is nickel used for? Metallic nickel is used in the manufacture of stainless steel and metal alloys. Nickel compounds are used for nickel plating, the manufacture of some batteries and some chemical catalysts. How can nickel affect human health? The most common harmful effect is allergic skin reactions due to direct contact with nickel-containing items such as some jewellery. Breathing large amounts of nickel compounds in nickel refineries can cause chronic bronchitis and lung and nasal sinus cancers. Nickel compounds are classified as carcinogens. Exposure can occur through eating food or drinking water containing nickel and by skin contact with soil or metals containing nickel. Exposure may also occur through breathing contaminated air and smoking tobacco containing nickel. What is the degree of risk? The National Environment Protection Council of Australia provides a soil nickel limit of 600mg/kg for the protection of human health, for residential use.
Cadmium	What is cadmium? Cadmium is a naturally occurring element and all soils and rocks contain some cadmium. Cadmium is found in coal and mineral fertilisers. What is cadmium used for? Cadmium is used in batteries, pigments, metal coatings and plastics. How can cadmium affect human health? Breathing high levels of cadmium can damage the lungs. Ingestion of contaminated food or water can irritate the stomach. Long-term exposure can lead to a build up of cadmium in the kidneys and cause kidney disease. Exposure to cadmium is mostly of an occupational nature and associated with industries making cadmium products. Breathing cadmium in cigarette smoke doubles the average daily intake. What is the degree of risk? The National Environment Protection Council of Australia provides a soil cadmium limit of 20mg/kg for the protection of human health, for residential use.