Report One: Cadmium in New Zealand Agriculture
Chapter 1: Setting the context - an introduction to the cadmium issue
Background to the Cadmium Working Group
The issue of cadmium in agricultural soils is not new, or unique to New Zealand. Since 1990, approximately forty peer-reviewed papers have been published in the scientific literature which examines aspects of cadmium in New Zealand agriculture. However, recent interest in the topic was sparked by an Environment Waikato report looking at cadmium levels in agricultural soils in the Waikato region.
Subsequently, it was considered appropriate to conduct a wider "stock take" of the cadmium issue at a national level. Further work was necessary to estimate the extent of cadmium accumulation in New Zealand agricultural soils, and to assess the likelihood and magnitude and consequences of any ensuing risks.
At a meeting in May 2005 of the Chief Executives’ Environment Forum1, a grouping of chief executives from central and local government supported a proposal to establish a Cadmium Working Group, with membership from central and local government, and representatives from industries directly affected by the issue. The group was charged with undertaking updated cadmium ‘stock take’, to explore the issues and risks relating to cadmium in New Zealand agriculture and food systems, and to develop and assess policy options for managing any risks.
The Cadmium Working Group’s Terms of Reference require the production of two reports (of which this is the first).
The first report would scope, at a national level:
- the extent of cadmium accumulation throughout the country, including source and sinks;
- the variation between different regions, types of agriculture;
- the implications of such accumulation for trade, future soil use and other issues deemed relevant;
- the issue of appropriate national standards and existing guidelines for cadmium in agricultural soils, noting the current responsibilities for standard setting of public bodies such as the Ministry for the Environment and New Zealand Food Safety Authority;
- an assessment of the risks and implications.
The second report is to be a solutions report, outlining policy options to address the issue. This report would consider appropriate options for management of cadmium, and provide an assessment of these options.
Membership of the Cadmium Working Group
The cadmium working group comprises senior representatives from the following organisations.
Horticulture New Zealand
Horticulture New Zealand is an alliance of the former NZ Fruitgrowers’ Federation, the NZ Vegetable and Potato Growers’ Federation and the NZ Berryfruit Growers’ Federation, which now represents 7,000 commercial fruit and vegetable growers. It aims to provide strategic leadership, raise the industry’s profile, to advocate on behalf of the horticulture sector and address issues which impact on business.
http://www.hortnz.co.nz/
Dairy Insight
Dairy Insight co-ordinates and funds "industry good" activities on behalf of all dairy farmers, who pay a levy based on a percentage of their milksolids production. Dairy InSight's focus is on providing industry leadership, in order to help make dairy farming more profitable and sustainable in the future.
www.dairyinsight.co.nz
Fonterra
Fonterra is a leading multinational dairy company, owned by 11 600 New Zealand dairy farmers. It is the world's largest exporter of dairy products, exporting 95 percent of its milk production. Fonterra also manufacturers and markets a vast range of dairy products and ingredients, which are sold in 140 countries around the world, and funds research and advocacy for the dairy sector.
www.fonterra.com
Meat & Wool New Zealand
Meat & Wool New Zealand is an industry body, funded by livestock and wool producers through levies. It promotes New Zealand red meat internationally and domestically, advocates for the extension of trade access for New Zealand wool and red meat; funds research and development, and provides wool technical advice.
http://www.meatandwoolnz.com
New Zealand Fertiliser Manufacturers’ Research Association (Fert Research)
Fert Research funds research into fertiliser and agriculture, liaises with a range of groups including government, regulatory bodies, industry, and research organisations, and also provides information on fertiliser use and nutrient management.
http://www.fertresearch.org.nz
Environment Waikato (EW), Environment Canterbury (ECAN) and Greater Wellington (GW)
These are regional councils, established under the Resource Management Act 1991. Regional Councils are responsible for environmental management and planning in their regions, including the management of the effects of use of freshwater, coastal waters, air and land, biosecurity, river management, regional land transport planning and civil defence.
http://www.ew.govt.nz/; http://www.gw.govt.nz/; http://www.ecan.govt.nz/
Ministry of Agriculture and Forestry (MAF)
The Ministry of Agriculture and Forestry informs, advises, regulates and delivers services relating to the agriculture, forestry, rural affairs, biosecurity and food safety portfolios. MAF’s mission is to enhance New Zealand's natural advantage. MAF does this by: encouraging high-performing sectors; developing safe and freer trade; ensuring healthy New Zealanders; and by protecting our natural resources for the benefit of future generations.
http://www.maf.govt.nz
New Zealand Food Safety Authority (NZFSA)
The New Zealand Food Safety Authority (NZFSA) administers legislation covering food for sale on the New Zealand market, primary processing of animal products and official assurances related to their export, exports of plant products and the controls surrounding registration and use of agricultural compounds and veterinary medicines. NZFSA is the New Zealand controlling authority for imports and exports of food and food-related products.
http://www.nzfsa.govt.nz
Ministry for the Environment (MfE)
The Ministry for the Environment is the Government's principal adviser on the New Zealand environment and international matters that affect the environment. MfE has taken a central role in developing policy relating to contaminants in the environment, and developed a series of best-practice guidelines to assist local authorities and environmental consultants in the management of contaminated land.
http://www.mfe.govt.nz
The Cadmium Working Group’s approach to risk assessment
The Cadmium Working Group’s first report is essentially a risk assessment. Risk assessment is a systematic evaluation of a particular risk, which is then used to inform decisions around what kinds of actions, if any, are needed to manage the risk. It seeks answers to the question: “how likely is it that damage will be or has been done by the hazard?”
Risk assessment is one component of the larger process known as risk management. The risk assessment provides the crucial information on which decisions about how to manage the risk can be made. The likelihood of adverse impacts on people, the environment or the economy, will inform decisions on whether intervention is required, and if so, what kinds of intervention. This stage of risk management is when policy considerations come into the process.
The social, economic, political context will usually be considered when assessing risk management options and value judgments may be made. The magnitude of the risk can be weighed against other considerations, such as the benefit from the activity generating the risk, social and political acceptability, and the cost effectiveness of treatment options.
The second report will correlate to the stage of "risk management option assessment", in which policy options to treat or manage the risk are evaluated.
The scope of the Cadmium Working Group’s risk assessment
The Terms of Reference state that the Group’s risk assessment is to consider the risks from cadmium in agricultural soils, to New Zealand agricultural and food systems. "Agricultural systems and food systems" is taken to encompass export trade and also future land use flexibility, as these are integral considerations to New Zealand agriculture.
In terms of potential human health impacts from cadmium, this report focuses on the dietary intake of cadmium. This is because the main exposure of the general populace to cadmium is in the diet. Specific, localised risks to small sectors of the population, such as occupational safety and health risks are not considered in this report.
Very little is known about the potential environmental impacts of cadmium accumulation. Monitoring of groundwater and freshwater has not shown evidence of increasing cadmium levels. However, very little monitoring for cadmium in water is carried out. It is possible that cadmium inputs to soil from fertiliser could accumulate in receiving freshwater sediments. The environmental impacts of cadmium in broader natural ecosystems are outside the scope of this report.
Cadmium in brief
Cadmium is a naturally-occurring, non-essential heavy metal which is present at low concentrations in air, water and soils. Cadmium has uses in industrial production, and is also present as an impurity in some non-ferrous metals (zinc, lead and copper), iron and steel, fossil fuels, cement and phosphate fertilisers.
Cadmium levels in the environment vary widely. Cadmium cycles in the environmental between air, water, soils, living organisms, sediments, rocks and minerals. In surface environments and over human timescales, air and water act as transport routes for cadmium, whereas soils and sediments act as cadmium sinks.
Air
Natural sources of cadmium to the atmosphere include forest fires, volcanoes, sea-salt spray, and wind-borne soil particles. Cadmium is present, therefore, in background "ambient" air, as well as in higher levels in air carrying industrial emissions or cigarette smoke. Globally, the main anthropogenic sources of cadmium emissions to the atmosphere are non-ferrous metal production, waste incineration and fertiliser manufacture (Nriagu JO and Pacyna JM; 1988).
Soil
In soils, cadmium originates from both natural and human-derived sources. Natural sources include the underlying bedrock or parent material. Human-derived inputs of cadmium to soil include the application of sewage sludge, manure and phosphate fertiliser. Anthropogenic discharges of cadmium to the atmosphere also contribute to cadmium levels in soil, as the cadmium settles onto land and water. In heavily industrialised parts of the world, cadmium in the atmosphere is often a significant source of cadmium input into soil. In New Zealand, the main source of human-derived cadmium to agricultural soils is phosphate fertiliser (Roberts et al, 1997).
Water
Cadmium exists naturally in small amounts in both freshwater and in the oceans. Cadmium may enter aquatic systems through weathering and erosion of soils and bedrock, atmospheric deposition, direct discharge from industrial operations, leakage from landfills and contaminated sites, and the leaching of fertilisers and biosolids from agriculture.
Cadmium and health
Cadmium can have adverse effects on human health, at high levels of exposure over a short period (acute exposure), or at low levels over a long period (chronic exposure). Most exposure of New Zealanders to cadmium occurs through low-level concentrations of the metal in food, or cigarette smoking. Cadmium accumulates in the bodies of animals, including humans, and so the amount of cadmium stored in the body increases with age. However, the New Zealand Food Safety Authority has estimated the amount of cadmium in the diet of the average New Zealander is at a level far below that which would cause adverse health effects (Vannoort RW & Thomson BM (2005) (this is discussed in more detail in Chapter 4).
Agriculture, fertiliser and New Zealand’s economy
Agriculture and New Zealand’s economy
More so than most other developed countries, New Zealand’s land-based sectors are strongly export orientated, have very low import protection, and are not supported by export or production subsidies (MAF, 2005b). Therefore, the fortunes of New Zealand’s agriculture are very much subject to conditions in international markets.
New Zealand’s economy relies heavily on agriculture2, it is the largest export earner, which earns 52 percent of the country’s total merchandise export value (year to June 2004). The total gross revenue from the agriculture sector, from the year ended March 2004, was estimated at $16.8 billion. This equates to about 13 percent of New Zealand’s Gross Domestic Product. Agriculture is also a growing industry; by 2008 the total gross revenue earned by the sector is projected to increase by about 9 percent, to $18.3 billion (MAF, 2005b).
The agricultural sector is the only major industry in New Zealand with world class economies of scale, global market reach, and world leading technological capabilities. New Zealand is the world’s largest exporter of dairy products, sheep meat and venison, second in kiwifruit, a major player in apples, and the fourth largest beef exporter (MAF, 2005). All this means that agriculture is a major driver of the New Zealand economy, fuelling many other businesses, such as manufacturing and processing and indirectly contributing to the retail and service sectors.
Agriculture dominates land use in New Zealand, as it does in many other countries globally. Most New Zealand agriculture is based on extensive pasture systems with animals grazed outdoors all year round. Between 1986 and 2002, the total amount of land farmed as dairy farms increased by 47 percent, reflecting the high economic returns from dairy in recent years. There are now approximately 2 million hectares (out of a total land area of 27 million hectares) under dairy farming in New Zealand (Statistics New Zealand, 2006; p 5). The area in sheep and beef farming has declined over the same period, and in 2002 stood at about 10.3 million hectares (ibid). The area under horticulture has expanded rapidly over the last fifteen years, but occupies about 1 percent of all land in agricultural use.
Fertiliser and agriculture
New Zealand’s soils tend to be naturally low in the four major nutrients required for plant growth: nitrogen, phosphorus, potassium and sulphur. As a result, on most soils, high levels of plant growth can only be achieved and maintained with nitrogen-fixing legumes (such as clover) and significant inputs of fertilisers. In some areas, planted forests are also bolstered with fertiliser. It is estimated that without the extra soil nutrients provided by fertiliser, New Zealand’s soils would only be able to support between 25 and 50 percent of the current number of animals grazed or crops grown (Statistics New Zealand, 2006). In other words, fertiliser use underpins a significant proportion of New Zealand’s economic production.
Dairy farming requires significantly more fertiliser per unit area than most other animal production land use types, because milk production depends on intensive grazing on high yielding pastures, which are maintained by inputs of fertiliser. Therefore, the trend towards converting land to dairy from other uses is contributing to growing rates of fertiliser use.
Phosphorus is an essential element for plant and animal nutrition. Cadmium is present as a naturally-occurring contaminant in phosphate rock, from which phosphate fertilisers are made.
New Zealand has no natural reserves of phosphate rock, and so all phosphate is imported largely from Morocco. The cadmium levels in phosphate rock vary widely depending on the source location. Worldwide, sources of low-cadmium phosphate rock are very limited and not currently available to New Zealand manufacturers.
New Zealand’s geography and geology
An important part of the New Zealand context is this country’s geography, geology, and the properties of the soil itself. These natural conditions influence the way in which cadmium accumulates, and becomes available for uptake by plants and consumed by animals and humans. Chapter 3 of this report reviews the current scientific literature on the interactions between natural conditions and other factors, which influence the bioavailability of cadmium to humans, plants and animals.
In general, the soils of New Zealand differ significantly from those of Europe and North America. Soil types in New Zealand are considered very diverse, despite the small size of the country (McLaughlin et al, 2000). New Zealand soils are geologically young and therefore less weathered, and have relatively high organic matter contents compared to similar soils in most other countries (ibid). Variable charge minerals (mainly hydrated oxides of iron and manganese) form an important component of many New Zealand soils, whereas in North America and Europe, many soils are dominated by permanent charge minerals (for example, clays) (ibid).
Many New Zealand soils are also classified as being highly acidic. Soil acidity, the nature and type of adsorptive phases in a soil, and presence or absence of competing elements (such as zinc) or complexing agents (such as fulvic acid) all play a role in determining how cadmium will behave in the environment, and therefore, the ease with which it may enter the food chain. Due to low-cadmium phosphate being used in the US, accumulation of cadmium from fertilisers does not appear to pose such an issue in the US as in Australia, New Zealand, and parts of Europe (McBride and Speirs, 2001).
The New Zealand climate is also highly variable, which again influences the behaviour of metals in soil, and therefore accumulation rates and bioavailability. Rainfall and temperature vary markedly between different parts of the country.
Chapter summary
Cadmium is a naturally-occurring, non-essential heavy metal which is present at low concentrations in air, water and soils. Both acute and chronic cadmium exposure can have adverse health effects on people. In New Zealand, industrial exposure to cadmium is rare, and so the main source of cadmium for New Zealanders is in tobacco products or food. Low levels of cadmium in the diet can accumulate over a person’s lifetime to reach levels at which they may begin to affect health. The New Zealand Food Safety Authority has estimated the amount of cadmium in the diet of the average New Zealander is at a level far below that which would cause adverse health effects.
Phosphate fertilisers contain cadmium as a trace impurity and cadmium tends to accumulate in soil with repeated application of phosphate fertiliser. Accumulation rates in soils will vary between regions of New Zealand due to differences in land use history, phosphate fertiliser cadmium content, total fertiliser use, soil types, climate, and a number of other variables. Cadmium can cause adverse animal and human health impacts at high levels or at lower levels if exposure occurs over a prolonged period.
There are three key threads to the New Zealand context relating to cadmium in soils, which influence the consideration of this issue. Firstly, the dominance of agriculture in New Zealand’s economy. Secondly, agricultural production is underpinned to a large extent by phosphate fertiliser, a major source of cadmium into agricultural soils. There is currently no cost-effective or practical method of removing it. Low-cadmium phosphate rock is either unavailable or difficult and more expensive to source. The third issue is the importance of the international trade to New Zealand agriculture and economy, which depends in turn on factors such as consumer demand, international regulation, and the wider economic and geopolitical situation.
In order to assess and mitigate any risks associated with cadmium, the Chief Executives’ Environment Forum established a Cadmium Working Group, to investigate and assess the potential risks surrounding cadmium in New Zealand agriculture and food systems, and to develop responses as required.
There are two basic approaches to assessment of cadmium: a "risk based" approach and a "mass balance" approach. The Cadmium Working Group used and promotes a risk based approach.
References
Canadian Food Inspection Agency (2004). “Approaches to Risk Assessment”. Accessed October 2005 from www.nvri.gov.tw
European Commission (2004). Working document relating to the modified draft proposal for a regulation on cadmium in fertilisers. Brussels.
Fergusson JE; Hayes RW; Tan SY; and Sim HT (1980). Heavy metal pollution by traffic in Christchurch, New Zealand: lead and cadmium content of dust soil and plant samples. “New Zealand Journal of Science”, Vol. 23, pp 293-310.
Graham BWL (1980). The industrial use of cadmium in Auckland, New Zealand. “Occupational Health (Australia and NZ)” Vol. 2, pp 13-16.
Graham BWL (1985). Exposure to heavy metals in the workplace. “Journal of the Royal Society of New Zealand”, Vol. 15, No. 4, pp 399-402.
Gray CW; McLaren RG; and Roberts AHC (2003). Cadmium leaching from some New Zealand soils. “European Journal of Soil Science”, Vol. 54, pp 159-166.
Kim N (2005). Cadmium Accumulation in Waikato Soils: Final Draft (Unpublished report). Environment Waikato, Hamilton.
Landcare Research (1999) “Risk Assessment for Contaminated Sites in New Zealand” [framework based on Australia’s National Environmental Protection (Assessment of Site Contamination) Measure, 1999]. http://contamsites.landcareresearch.co.nz/
McBride MB; and Spiers G (2001). Trace element content of selected fertilizers and dairy manures as determined by ICP-MS. Communications in Soil Science and Plant Analysis, Vol 32 (1&2), pp 139-156.
McLaughlin MJ; Hamon RE; McLaren RG; Speir TW; and Rogers SL (2000). Review: A bioavailability-based rationale for controlling metal and metalloid contamination of agricultural land in Australia and New Zealand. In “Australian Journal of Soil Research”. Volume 38. 1037-86. CSIRO Publishing, Australia.
Ministry of Agriculture and Forestry (2003). “Contribution of the Land-based Primary Industries to New Zealand’s Economic Growth”. MAF, Wellington.
Ministry of Agriculture and Forestry (2005). “Agriculture, Forestry, Rural Affairs: Briefing for Incoming Minister”s. MAF, Wellington.
Ministry of Agriculture and Forestry (2005b). “Situation and Outlook for New Zealand Agriculture and Forestry: May 2005 Update”. MAF, Wellington.
Molloy R; McLaughlin M; Warne W; Hamon R; Kookana R and Saison C (2005). “Background and scope for establishing a list of prohibited substances and guideline limits for levels of contaminants in fertilisers”. CSIRO Land and Water, Australia.
Nordic Council of Ministers (2003). Cadmium Review. www.norden.org
Nriagu JO & Pacyna JM (1988). Quantitative assessment of worldwide contamination of air, water and soils by trace metals. In “Nature”. Vol. 333, No. 6169, pp 134-139.
Renner R (2000). Sewage sludge, pros and cons. In “Environmental Science and Technology”. Vol 34, Issue 19.
Roberts AHC; Longhurst RD & Brown MW (1997). Cadmium accumulation in New Zealand pastoral agriculture. “Biogeochemistry of Trace Metals”, pp 1-41. Science Reviews, Northwood, UK.
Schulte-Shrepping KH & Piscator M (1985). Cadmium and cadmium compounds. In Gerhartz W (Ed.) “Ullman’s Encyclopaedia of Industrial Chemistry Vol. A4”, 5th edn. Verlagsgesellschaft, Germany.
Sharma RP. (1981). High blood and urine levels of cadmium in phosphate workers: a preliminary investigation. “Bulletin of Environmental Contamination and Toxicology”, Vol. 26, No. 6, pp 806-809.
Statistics New Zealand (2006). Fertiliser Use and the Environment. www.stats.govt.nz
Vannort RW & Thomson BM (2005). “2003/04 New Zealand Total Diet Survey”. New Zealand Food Safety Authority, Wellington.
1 The Chief Executives Environment Forum is a group of chief executives from regional government and central government departments that have strong interests in environment and resource management - Environment, Agriculture and Forestry, Economic Development, Fisheries, Conservation, Transport, Internal Affairs, State Services Commission, Department of Prime Minister and Cabinet, and Te Puni Kokiri. The forum is convened by the Ministry for the Environment, and meets four times a year to exchange information and views, plan joint work programmes, agree on complementary activities, and resolve problems. (Source: MfE website, http://www.mfe.govt.nz/publications/about/briefing-oct05/html/page3.html, accessed September 2006).
2 Agriculture is defined here as including both on-farm production and first-stage processing of food and fibre. Horticulture is a component of agriculture.
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