Taking into account the legal instruments listed in section 6.5, there are still several gaps in many countries’ capacity and activities to manage soil pollution. Environmental policies in many countries in this region are still young. However, Australia’s National Environmental Management Plan, which was established in 1999, is an exception. This legislative instrument contains risk-based numerical criteria for assessing sites, taking into account the nature and behaviour of contaminants in the environment and exposure pathways. It is one of the most comprehensive guidelines on establishing soil pollution criteria for a range of polluting activities, considering both human health and the environment.
For most countries, soil pollution prevention is a priority in legislation and policymaking. In most cases, as polluting sources are varied, soil pollution is not legally defined or recognized, and instead, only agricultural productivity and soil erosion mitigation are given priority. In several countries industrial activities that pollute soil are not consistently regulated, with the emphasis being placed only on particular contaminants such as POPs. Some countries have specific legislation on POPs, but implementation of such legislation in developing countries in the region is challenging. Implementation of some contaminants such as PFOS is globally challenging, but developing countries in the Asia–Pacific region have not begun to look for them in the environment.
In the absence of clearly defined soil polluting activities, opportunities for developing management strategies, monitoring plans, compliance and enforcement activities are limited. For example, at the political level in Bangladesh, there is no specific statement for the control of soil pollution. However, in its National Environmental Policy 2018, under point 3.5 agriculture, it states that organic farming should be prioritized; the use of organic fertilizers and pesticides should be encouraged, while the use of chemical components should be controlled to minimize “agricultural pollution” and “soil pollution”.
The Taiwan-EPA has developed regulations including control standard levels (CSL) for trace elements, pesticides and organic contaminants in soil and groundwater based on the “Soil and Groundwater Pollution Remediation Act (SGWPR Act)” (Taiwan-EPA, 2019c). The CSL provides the basic rules for setting the remediation objective of polluted site. The main gap is securing funds to meet the cost of cleaning up the site. Therefore, the Taiwan-EPA has started to propose a risk-based approach for remediation projects to evaluate the risks to environmental quality and human health. Two cases are examined to reflect these gaps, (i) a natural serpentine soil rich in chromium and nickel, and (ii) an arsenic polluted soil from the Guangdu plain near the city of Taipei (Apollo-Technology-Company, 2013, 2014; Hseu et al., 2015; Su et al., 2014).
Natural serpentine weathering alluvial soils, spread over more than 300 ha in eastern Taiwan, had elevated total chromium and nickel concentrations ranging from 200 mg/kg to more than 1 000 mg/kg, exceeding the CSL of 250 mg/kg for chromium and nickel in rural soils. The bioavailability of chromium and nickel is less than 1 percent of the total concentration of chromium and nickel in soil. There are no additional health risks from rice and vegetable production due to these concentrations of chromium and nickel so the Taiwan-EPA classified these soils as not polluted (Apollo-Technology-Company, 2013, 2014; Hseu et al., 2015; Su et al., 2014).
The CSL for arsenic in soil is 60 mg/kg. An area of approximately 200 ha in the volcanic alluvial soils of the Guangdu plain was initially identified as being potentially polluted as it had arsenic concentrations ranging between 60 mg/kg to 500 mg/kg. However, the main cause of the high arsenic concentrations was the dissolution of the volcanic rocks of the volcanic National Park (which are rich in arsenic and lead) into the river water. The bioavailability of arsenic of this soil was very low due to the high amounts of amorphous iron and aluminium in the volcanic soils. Concentrations of arsenite or arsenic(III) in brown rice are all below 0.2-0.3 mg/kg and there is no health risk. On the basis of the absence of health risks and the natural origin of the arsenic, the Taiwan-EPA has determined that the soils should not be classified as polluted (Apollo-Technology-Company, 2013, 2014; Hseu et al., 2015; Su et al., 2014).
These two “success cases” show that the high total concentration of chromium and nickel from serpentine alluvial soils or arsenic from volcanic soils have no artificial pollution sources and pose no risk to environmental quality and human health. The Taiwan-EPA by taking a risk-based approach and not slavishly following the CSL has determined that public health and the environment were not threatened by these two sites. It has saved both time and resources that can be focused on polluted sites whose remediation will benefit human health and the environment. Finally following communications programmes with stakeholders in Taiwan Province of China, academia, scientists, and the NGO community have accepted the new risk-based methodology for assessing contaminated sites. This is a major step forward in bridging knowledge gaps between different stakeholder groups in Taiwan (Apollo-Technology-Company, 2013, 2014; Hseu et al., 2015; Su et al., 2014).
Although very limited research has been conducted on organic contaminants (including POPs) in the soils of Bangladesh, the Department of Environment of the Ministry of Environment and Forests of Bangladesh (BGD-DoE, 2007) has set some goals to combat the adverse effects of POPs. In accordance with the National Implementation Plan, emphasis has been placed on enhancing national capacities (raising public awareness, improving management and technological capacities, and allocation funds) to combat POPs (Islam et al., 2018b).
In Sri Lanka, several gaps were identified in the policy and regulatory framework to manage and mitigate soil pollution. The main gaps include: financial restrictions imposed on farmers for land restoration work; limitations in the creation of key institutions and/or integration between institutions for the development of strategic plans; and the lack of capacity of its regulatory services.
Policy for the prevention, management and regulation of contaminated soils in many countries of the region is inadequate. There are gaps in science as well as inadequacies in policy development that is response to emerging science. Slow or incomplete transfer of knowledge from scientists and enforcement agencies to policymakers one of the main reasons for this gap.
Each year, the risk assessment of newly added or identified chemicals is technically slow and, as a result, their occurrence in the environment, often referred to as emerging contaminants, is of great concern to the public and regulators. This is a science gap but countries in the region can benefit from the research and experience of those in other regions.
Examples of these emerging contaminants are PFAS, for which there are many knowledge gaps related to their toxicity and threshold values in various soils in this region. Most scientific studies on these chemicals are being undertaken for two PFAS compounds, PFOS and PFOA (Cohen Hubal, 2019). However, in this region, Australia and New Zealand are taking the lead in developing draft guidelines for PFAS in the environment, including soil (HEPA, 2019). The draft report was released for consultation and improvement after its first version in 2018. The Australian Government has also taken initiatives to promote research on these compounds in the environment by providing research grants. However, there is a lack of data in the region that can be used as the basis for country-specific policies for the identification, management and mitigation of soil pollution by PFAS.
Microplastics are another emerging contaminant in the soil. Studies and publications with extensive scientific evidence on plastic pollution in the marine ecosystem have been used to influence policy and thus raise awareness to reduce the use of plastics. However, plastic particles (i.e. synthetic polymer particles less than 5 mm in diameter, in soil remain largely unknown in terms of identification, impact and fate in soil) especially in agricultural soils (Zhang and Liu, 2018) and road dust (Yukioka et al., 2020). These plastics include microbeads disposed on the soil or weathered plastic mulch from plastic sheeting used in agricultural activities. Wijesekara et al. (2018) reported that these contaminants could be either beneficial or harmful to the soil microbial community. They showed that the presence of particulate plastic could reduce copper toxicity by sorbing the trace elements onto the organic fraction of the plastics. However, this effect could be one-sided, while the leaching of trace elements (e.g. zinc) from these plastics or the migration of microplastics to the nearby aquatic environment, including groundwater, would cause serious problems for aquatic biota. It could eventually have an adverse effect on human health with its transference through food chains (Bradney et al., 2019; Hurley and Nizzetto, 2018).
In response to climate change, soil properties and processes are likely to change and alter the dynamics of chemical contaminants in soil systems (Biswas et al., 2018). Soil organic matter plays a significant role in the retention, transport, and exposure of both inorganic and organic contaminants in soil. Extreme events resulting from climate change, such as prolonged drought, extreme rainfall, and soil warming, alter the dynamics of soil organic matter (Biswas et al., 2019). However, only a few short-term laboratory-based studies are available in the current scientific knowledge, which presents the following gaps:
The lack of generally accepted threshold values for toxicity assessment of priority and emerging contaminants is another gap identified in the region. For example, for assessing arsenic soil toxicity, there are certain limitations that have not yet been overcome (Heikens, 2006). Arsenic is often spiked into the soil and then the toxicological assessment is conducted; however under field conditions arsenic accumulates over a long time of period, which cannot be represented by this assessment method. Arsenic is also added to irrigation water, but this method neglects the fact that arsenic levels in irrigation water in the field are relatively constant and that arsenic is slowly added to the soils over a period of many years. Often, total arsenic is taken into account for soil studies, without taking into account the arsenic natural concentrations and speciation in the soil matrix.
The above-mention scientific gaps and more emerging scientific evidence are likely to be derived from lack of political will as well. For example, generally, the PICs suffer from a number of gaps between science and policymaking. There is a lack of understanding about soil pollution in the policymaking area. There can be pressure on policymakers to support industries that are contributing to the country’s economy despite the risks that they pose to the environment and public health. There is also a lack of adequate regulation that could bridge these gaps. There is a need to expand efforts to understand the source, pathways of contaminants and public exposure. The PICs do not maintain registers or records of polluting activities and related contaminants. This is especially pertinent for Fiji, Papua New Guinea, New Caledonia, Vanuatu and the Solomon Islands, where industrialization and mining are of medium intensity. Due to the lack of data and information to establish links between sources, pathways and receptors, there is a significant knowledge gap that impedes the prioritization of activities to mitigate the potentially adverse effects of contaminant exposure in the PICs. With respect to trace element pollution, for example, the literature provides evidence that there may be a potential link between the source-pathway-receptor that needs to be studied in detail. A regional database can assist national and regional efforts, given the commonalities among some of the PICs. A further weakness is that regional strategies and national legislation do not provide for remediation action.
In contrast, political will is relatively more prevalent where there is a clear collaboration with international programs and aid on pollution control. For example, SPREP has assisted in the development of generic legislation to assist in the management of POPs. Another good example is the European Union Pacific Waste Management Programme (PacWastePlus) implemented via SPREP. This program addresses both the cost effective and sustainable management of waste and pollution. Countries are able to prioritise issues of concern and receive assistance on the national management of the issue. Uptake of such initiatives is dependent on the political will on individual states underpinned by scientific evidence.