Plastic released to the environment poses a substantial threat to ecological and human health globally1,2. This is reflected in rising concern, internationally; according to Espen Barth Eide and quoted in the Washington Post on 8 February 2022, countries around the world are “increasingly seeing [plastic pollution] as a top-level threat”.
In addition to being Norway’s Environment Minister, Eide also led discussions at the recently concluded (2 March 2022) 5th session of the United Nations Environment Assembly to establish an Intergovernmental Negotiating Committee that will work towards a legally binding global agreement to mitigate plastic pollution. 175 nations signed-up to the agreement in Nairobi, which targets the full cycle of plastic, production-(re)use-disposal. The aim is to have a fully legally-binding agreement by the end of 2024.
The agreement is likely to result in caps on the production and disposal of plastic, similar to the voluntary limits on CO2 emissions linked to the 2015 Paris Accord. Determining those caps requires data on how much plastic is produced, how much ends up as waste and where, what chemicals are incorporated within and attached to plastic waste, and, from a planetary health perspective, how much plastic pollution can the Earth system sustain before critical processes, such as the maintenance of soil fertility and ocean productivity, are altered, possibly irreversibly3.
While the prospect of an international agreement aimed at reducing and even reversing plastic pollution has to be a good thing, we know from experience that reaching global agreements where the environment is concerned and where there is a complex array of competing, vested interests at play, is generally a long drawn out process. This process will be made all the more difficult because, for most parts of the world, reliable forms of data are lacking or at best very scarce ~ and this is particularly the case for micro-plastics. Micro-plastics are of particular concern, because they can remain suspended in the atmosphere for several days (atmospheric micro-plastics, or At-MPs) and this enables their transport over large distances and across international boundaries. Their small size also makes micro-plastics both difficult to detect in sites of deposition and accumulation, and easy to ingest and thus pass into and along food chains. Once ingested and as with other forms of fine particulate matter, levels of micro-plastics and other toxins and pathogens that might be incorporated or attached to the surface of the particle, can accumulate and magnify through food chains, thereby presenting a direct, cumulative risk to human health and food security.
Nowhere is the problem of a plastic data deficit more true than in Southeast Asia, which is widely regarded as a hotspot of global plastic pollution.
This shortcoming and the uncertainties concerning the human and planetary health risks that arise from it, together with the complex of competing interests and stages of development of countries involved, are likely to hamper the development and effective implementation of any global agreement aimed at mitigating and ideally reversing rising levels of plastic pollution ~ just as they have international attempts to limit global warming.
The shortcoming does, however, create exciting opportunities for research aimed at addressing the data deficit. Such research would improve our understanding of plastic pollution in all its forms, and the risks of our long-term exposure, both outdoors and indoors, to micro-plastics in particular.
Jahnke, A. et al. Reducing Uncertainty and Confronting Ignorance about the Possible Impacts of Weathering Plastic in the Marine Environment. Environ. Sci. Technol. Lett.4, 85–90 (2017).
Macleod, M. et al. The global threat from plastic pollution. Science (80-. ).373, 61–65 (2021).
Persson, L. et al. Outside the Safe Operating Space of the Planetary Boundary for Novel Entities. Environ. Sci. Technol.56, 1510–1521 (2022).
Figure (from Steffan et al. (2015) Science, 347, issue 6223 #1259855) illustrates the current status of the control variables for seven of the nine planetary boundaries. The green zone is the safe operating space (below the boundary), yellow represents the zone of uncertainty (increasing risk), and red is the high-risk zone. The planetary boundary itself lies at the inner heavy circle. Control variables (see text below) have been normalized for the zone of uncertainty (between the two heavy circles); the center of the figure therefore does not represent values of 0 for the control variables. Processes for which global-level boundaries cannot yet be quantified are represented by gray wedges; these are atmospheric aerosol loading, novel entities, and the functional role of biosphere integrity.
Conceptually, planetary boundaries (PBs) define a safe operating space for humanity determined by the state of key biophysical processes that combine to regulate the stability of the Earth system. As the above figure from Steffan et al (2015) indicates, some of the nine PBs that are commonly referred to and their linked control variables (measurable parameters that represent the state of the PB) are relatively well-understood. For example, climate change and atmospheric CO2 concentration, and biogeochemical flows and nitrogen fixation rates. In these cases, the PB concept could be claimed to be having an influence over policy-making, for example in the setting of caps on CO2 emissions in order to mitigate climate change. Much uncertainty concerns the other PBs, however. Notable among these are novel entities (NEs), or new substances, new forms of existing substances and modified life forms that have the potential for unwanted geophysical and/or biological effects.
A paper just out (Persson et al. (2022) Environmental Science and Technology, 56: 1510-1521 – a publically accessible version of which is available below) reviews the scientific discussion centred upon attempts to define and quantify the PB for NEs, focusing in particular on plastic pollution as a component of chemical pollution. Chemical pollution generally is of particular concern because of a huge uptick in the production and release of a broad range of chemicals, including plastic, over the last 70 years or so. Global production of chemicals has increased 50-fold since 1950 ~ today there are an estimated 350,000 chemicals and mixtures of chemicals available to buy. We know very little about the long-term exposure risks of the vast majority of these and virtually nothing at all about potential synergistic effects nor their ability to bioaccumulate and biomagnify through the food chain. The vast majority of chemicals now in production have a synthetic origin – they do not naturally occur. Therefore, unlike control variables for other PBs such as CO2 and nutrients, there is no “natural” baseline against which to compare current levels and trends. We therefore have no idea just how much NEs the Earth system can withstand without a major shift towards a new operating state that in all likelihood will be less suitable (or “safe”) for humanity and the ecosystem services we are dependent upon. In other words, we have no idea where the tipping point for NEs might be.
Trying to control releases of one harmful chemical often simply results in increased releases of another chemical if the need for the non-harmful properties of the original chemical remain – the so-called “lock-in” effect. The lock-in effect becomes particularly serious when the replacement chemical subsequently turns out to be equally if not more harmful than the chemical it was designed to replace. The production and use sequence of CFCs, HFCs and HCFCs is an example of this. Lock-in effects also relate to our use of resources. Thus CO2 and plastics are both products of our use of fossil fuels (CO2 emissions result from our burning of fossil fuels, whereas 99% of the materials that go into plastics are from fossil fuels). If we reduce our burning of fossil fuels to generate power, thereby reducing CO2 emissions, will the fact that we are locked-into (economically dependent upon) a fossil fuel industry mean that the latter will start to invest even more in encouraging the use of (and therefore the need to produce more) plastic, thereby increasing plastic pollution? How do we avoid this lock-in effect?
The paper introduces the concept of an “impact pathway” and its use in defining control variables for NEs. There are major differences between countries in their abilities to monitor and manage production and releases of NEs. Even in technologically advanced countries, however, the current rapid growth in the production and release of NEs into the environment massively outstrips our ability to assess the ecological and human health risks posed. Given that we know so little about the impacts of NE releases and how much the Earth system can cope with, the authors of the paper argue for a precautionary approach to what is a transboundary, global problem. Just as we have developed and implemented policies aimed at net zero emissions of CO2, we need – the paper claims – to at least cap emissions of NEs at levels below tipping points in the Earth system. In order to do this, we need research on where those tipping points might be and how they might vary as a result of, for example, climate change.
Rather than just investing in the invention and production of new chemicals to meet our ever increasing needs, we also need to start investing much, much more in how existing and new chemicals are impacting and likely to impact ourselves and the world we share.
An air tanker drops retardant as the Lake Fire burns in the Angeles National Forest north of Santa Clarita, Calif., on Thursday, Aug. 13, 2020. (AP Photo/Noah Berger)
2020 seems to have been a particularly bad year for wildfires globally. Major fires that commenced in Australia in 2019 continued into the first few months of 2020. They were followed by wild (or biomass) fires in many other parts of the world, from the Amazon to the Arctic and from central Africa to California, and other states in western/northwestern US. Wildfires have a multiple of causes, of course, but climate conditions are often a major contributing factor. Perhaps unsurprisingly, an August 2020 paper in the journal Environmental Research Letters, available here, finds climate change to be important in increasing the likelihood of extreme late summer/autumn wildfire conditions across California. The authors note that a cocktail of environmental conditions (high temperatures, low rainfall, strong winds) have enabled the ignition and spread of wildfires. They use climate models to project future conditions, and find that continued climate change will further lengthen the period during which extreme fire weather occurs, and hence the most devastating wildfires (assuming there is still biomass left to burn!).
Is this how the world ends?
Given that major wildfires are perhaps even more likely, rather than less, in coming years – as a result of climate change but also as humans and their sources of ignition penetrate deeper into forested and peat lands, now is probably a good time to evaluate the effectiveness of our response. Here I would like to focus, in particular, on the chemicals that are used to limit the spread or reduce the intensive of wildfires ~ fire suppressant and retardant chemicals, in other words. These are the often brightly coloured substances that get air-dropped on and around wildfires – they are to fighting wildfires what chemical dispersants are to dealing with oil spills at sea. Just as we have begun to question the efficacy of chemical dispersants when dealing with a major oil spill it is probably useful to enquire about fire suppressant and retardant chemicals, and in particular whether they do more harm than good.
There are several types of fire suppressant (generally applied to a fire to reduce its intensity) and retardant (used to reduce the chances of a fire starting or spreading once started) chemicals. Fire suppressants generally reduce the temperature of the fire – water sprayed onto burning vegetation is an example, as are chemical foams. Foams are wetting agents that allow water to penetrate a surface more effectively, thereby allowing its more efficient use in suppressing a fire.
Fire retardants (e.g. Phos-Chek) are most often used in the creation of fire breaks – their application is aimed at reducing the combustibility of vegetation ahead (i.e. in front) of an advancing fire. They are therefore designed to persist in the environment rather than to degrade immediately. The most common retardants are a combination of water and either ammonium sulfate [(NH4)2SO4] or diammonium phosphate [(NH4)2HPO4] mixed with additives to thicken, reduce spoilage during storage and colour the liquid. The latter give fire retardants their bright colours – so that it is possible to see which parts of the landscape have already been treated, but also (I guess) to look good on the TV …. Retardants also include other elements to help reduce combustibility, including antimony, chlorine, bromine, boron. Chlorine and bromine are used in what are known as “halogenated retardants”.
A plane drops fire retardant on a wildfire in Fallbrook, Calif. (AP Photo/Gregory Bull)
Generally retardants are regarded as being non-toxic to humans and large mammals, at least in low concentrations. However, their toxicity to aquatic life, even at low concentrations, has long been known (e.g. Dietrich, 2013). Although retardants are meant for terrestrial use (spraying on forest and other combustible biomass) they can end up being washed into or inadvertently sprayed over aquatic ecosystems. Further, the toxicity of some of the chemicals used may be enhanced by the heat of, or through mixing with emissions from, the wildfire. At high temperatures, some halogenated retardants can form extremely toxic dioxins, for example.
And then there are the environmental effects of spraying ammonium sulfate and diammonium phosphate over large areas of vegetation and soil. Both are ammonium-based fertlizers, and therefore likely to result in environmental eutrophication and acidification. Ironically, depositing large amounts of fertilizer is likely to boost productivity in vegetation that survives the fire – resulting in increased loadings of highly-combustible litter, potentially adding to the intensity of any burn during the next fire-season ….
Given the current extent and intensity of wildfires and the likelihood that conditions that predispose biomass to burning will become more extensive, frequent and intense in coming years, chucking chemicals that only add to environmental pollution and its harmful effects at the problem seems neither desirable nor sustainable.
Much has been written over the past few months about the the relationship with the COVID-19 pandemic and air quality. Based on past experiences – e.g. the so-called Spanish Flu pandemic of 1918-1919 caused by a H1N1 virus – we know that the symptoms and effects of respiratory illnesses are made worse by poor air quality. We have feasible mechanisms that explain the link too – air pollution facilitates both the ability of a pathogen (such as a virus) to invade a human body, by damaging the epithelial cells that line the respiratory tract, and, once in, proceed to modulate the host’s immune response. Thus it is perhaps not so surprising that studies (e.g. by Wu et al.) have revealed a link between poor air quality and a high incidence of the most severe cases of and highest death rates due to COVID-19. Of course there are likely to be other factors at play too that are also linked to poor air quality, such as poverty, poor diet, inadequate access to health facilities etc. Therefore it is perhaps best to see poor air quality as an amplifier of the effects of existing inequalities.
A lot has also been written about the positive effects on air quality of lock-downs around the world in response to COVID-19. Reduced industrial activity and reduced travel (particularly in airplanes) have contributed to reduced pollution emissions, including those to the atmosphere. As a result, clear skies have been reported in many places where such experiences had become the subject of distant memories. But these positive effects are likely to be short-term, and unlikely to outlive lock-downs, as is already evident in some places that have seen something of a recovery in economic activity in recent weeks. They also come at a huge economic cost too, which itself will have profound, negative health effects ~ and could also reverse some of the pre-COVID-19 successes in dealing with some of the more intractable environmental problems, such as climate change, as governments focus more on the future health of national economies rather than existing international obligations. A recent article in Nature Sustainability (see here) focused on China makes the point very well that while lock-downs resulted in improvements in air quality those improvements were relatively small, were least in warmer, sub-tropical parts of the country (where a large proportion of China’s population and industry is located but where consumption of polluting fossil fuels for heating is generally lower) and came at huge economic cost. Hu et al., the authors of the study, go on to opine that the same improvements in air quality, but over the long term, could be made at a much lower cost through the implementation of anti-pollution measures targeted at individual large emitters of air pollutants.
Fortunately, when relatively short-term variations in air quality – due to, for example, lock-downs associated with disease pandemics or major sporting events such as the Beijing Olympics of 2008 – are placed in the context of air quality measurements over the longer-term, it seems that air pollution and its health effects have been reduced throughout much of China since 1997. The date 1997 is significant in China because it shortly precedes the Chinese Government’s declaration of war on air pollution in its capital, Beijing (see UN report here).
According to research recently published last month (August 2020) by Yin et al in Lancet Planetary Health it seems that improvements in air quality as a result of reductions in fine particulate matter (PM2.5) in the atmosphere have occurred across China since 1997 following implementation of a series of national and regional control measures. For example, the National Air Pollution Prevention and Control Action Plan was introduced in 2013, and this has led to widely observed reductions in ambient concentrations of PM2.5. Improvements in air quality, including indoor air quality, have also followed a ban on the use of coal for domestic heating and cooking.
Population-weighted mean ambient PM2·5 concentration in provinces of China in 1990 (A) and 2017 (B) (from Yin et al 2020)
Despite these improvements, however, the vast majority of people in China (about 80% according to Yin et al) still live in areas where air quality does not meet even the most basic World Health Organisation (WHO)’s recommended levels, and mortality rates linked to poor air quality although on the decline in many parts of the country remain high overall (over a million premature deaths due to air pollution in 2017, according to Yin et al). Major differences in mortality rates linked to air quality remain within China, presumably reflecting differences in socio-economic conditions, access to health facilities etc, with 12 provinces actually showing an increase in mortality rates over the ca 30-year long study.
China and indeed many parts of the world now stand at something of a crossroads with regard to air quality. Will recent improvements in air quality, either linked to COVID-19 related lock-downs or to policies and regulations implemented over the longer-term, be maintained into the future? Or will potentially highly polluting and health-threatening fossil fuels once again be returned to as the convenient engine of global economic growth, as they were following World War II? Such a return may now be taking place in China (see here).
Here are the student blogs for the Semester one AY2020-2021 version of GE3246 Environmental Pollution (August to November 2020) – note that up to the academic year 2021-2022, Environmental Pollution ran at level 3000. The content of the module has been enhanced and in-line with the module’s elevated level 4000 status.
The latest data on atmospheric concentrations of greenhouse gases (GHGs) released by the World Meteorological Organization (WMO)’s Global Atmosphere Watch and published in the 25 November 2019 issue (issue #15) of the WMO Greenhouse Gas Bulletin make for chilling reading. Issue #15 can be accessed at the bottom of this post.
The data for 2018 show an increase in concentrations for three key GHGs, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) over 2017 levels (Table 1). For two of the GHGs (CH4 and N2O) the rate of increase 2017-2018 is greater than the average rate of increase over the preceding decade, while for CO2 the increase is around the average rate of change for that same period. Positive radiative forcing attributed to the three key GHGs has increased markedly since pre-industrial times (pre-AD 1750). Thus radiative forcing attributed to increased concentrations of CO2 has increased by 147%, CH4 by 259% and N2O by 123% since pre-AD 1750.
Table 1: Global annual surface mean abundances (2018) and trends of key greenhouse gases from the GAW global GHG monitoring network. Units are dry-air mole fractions with 68% uncertainties shown. The data are based on an average of several stations around the world. There are relatively few stations for tropical latitudes.
Emissions of CO2, CH4 and N2O can persist in the atmosphere for relatively long periods. They are also therefore commonly referred to as “long-lived GHGs” (LLGHGs). One other group of pollutants are also considered as LLGHGs, the ozone-depleting chlorofluorocarbons (CFCs) together with hydrochloroflurocarbons (HCFCs), hydrofluorocarbons (HFCs) and sulphur fluorides, such as “deep voice gas” mentioned previously on the Environmental Pollution blog (see here ). Although atmospheric concentrations of CFCs have stabilised and even reduced in the last decade or so since implementation of the Montreal Protocol, levels of HCFCs, HCFCs and sulphur hexaflouride (SF6, deep voice gas) have increased (HCFCs were meant as an interim replacement for CFCs, with HFCs intended to replace HCFCs) (Figure 1). According to the WMO Greenhouse Gas Bulletin, radiative forcing of all LLGHGs combined has increase by 43% since 1990, with the 2018 level corresponding to an equivalent CO2 mole fraction of 496 ppm!
Figure 1: Changing atmospheric concentrations of halocarbons (CHFs, HCFCs and HFCs) and SF6.
Issue #15 of the WMO Greenhouse Gas Bulletin also refers to some neat work involving the measurement of different isotopes of carbon. Carbon in the environment occurs in the form of three isotopes ~ 12C (the most common), 13C and 14C (the least common). Establishing the relative ratios of these isotopes in the atmosphere provides an indication of the source of the carbon, and knowing the source can help explain the most likely cause of increased concentrations of carbon-containing GHGs in the atmosphere (notably CO2 and CH4). The figure at the top of this blog and repeated below as Figure 2 illustrates changes in anthropogenic (human) emissions, the atmospheric concentration of the 13C isotope and CO2 and the 14C content of the atmosphere since the mid-18th century. Some of the data are from direct measurements, whereas the earlier data relating to atmospheric composition are from carbon preserved in ice cores and tree rings. The figure shows that as human emissions of CO2 have increased (panel a) so too have concentrations of CO2 in the atmosphere (panel c). At the same time, both the relative proportions of 13C and 14C have declined. This is because CO2 emitted from the burning of fossil fuels is relatively rich in 12C, and massive emissions of 12C-enriched CO2 from the burning of coal and oil in particular have caused a relative decline in the proportion of the 14C and 13C isotopes in the atmosphere (the massive spike in atmospheric 14C around the beginning of the 1960s relates to the atmospheric detonation of atomic bombs). Variations in relative concentrations of the three carbon isotopes provide additional evidence that a large part of the increased CO2 in the atmosphere is from the burning of fossil fuels, and is therefore human in origin.
Figure 2: Variations CO2 emissions and atmospheric concentrations, and in relative proportions of 13C and 14C isotopes.
Finally, issue #15 of the WMO Greenhouse Gas Bulletin highlights the interesting trends shown by CH4 concentrations in the atmosphere. Following rapid increases during the 1980s and 1990s, atmospheric concentrations stabilised during the early 2000s. The stabilisation appears to have been short-lived, however, as by the late 2000s levels had started to rise rapidly again (Figure 3). Approximately 60% of CH4 emissions are linked to human activity (e.g. cattle farming, rice agriculture, and the burning of fossil fuels and living biomass – e.g. forests and peatlands). Once again isotopic measurements can help determine the source of CH4 in the atmosphere. Despite this, the cause(s) of the plateau and the renewed increase in atmospheric concentrations is(are) a focus of much debate among scientists at present.
Figure 3: Globally averaged CH4 mole fraction (a) and its growth rate (b) from 1984 to 2018. The red line in both panels is the monthly mean with the seasonal variation removed. The figure is based on observations made at 127 stations globally.
Hà Tĩnh Province in northern central Vietnam, economically one of the poorest parts of Vietnam, has been heavily featured in the news of late, after the bodies of 39 people – many thought to be from the province – were found in the refrigerated trailer of a lorry in Waterglade Industrial Park, about 25 miles east of central London. Following the tragedy much attention has focused on the criminal gangs and risks involved in people trafficking, and on poverty in parts of central Vietnam.
Hà Tĩnh Province, north-central Vietnam
Much less attention has been paid to the role of environmental disasters as a possible reason why the economically-marginalised might risk their own lives and the future of family members who they leave behind ~ the latter through borrowing the relatively large amounts of money (several times an annual income in rural central Vietnam) demanded by people-traffickers, with stay-behind-relatives left to pay-off any outstanding migrant loans.
Reuters “Postcards from a poisoned coast” report released towards the end of last week (29 October) highlights the role that pollution and other drivers of environmental change might have played in the disaster that befell the 39 migrants. While in no way excusing people trafficking and the criminals that profit massively from it, the report highlights that many rural livelihoods in Hà Tĩnh and surrounding provinces have been made all the more precarious of late by frequent environmental disasters. An increasingly precarious livelihood is a potential trigger in deciding to risk being trafficked for the promise of a better life far away. The Formosa Steel plant, owned by Taiwan’s Formosa Plastics, in Hà Tĩnh Province was in 2016 the source of one of Vietnam’s worst environmental disasters. The disaster involved the discharge of toxic waste directly into adjacent areas of sea via “a submerged pipe belonging to the Formosa corporation, 1.5km in length, buried under the seabed“. Hundreds of tons of fish died as a result, and this loss and resultant bans on the sale of fish because of concerns over food safety disrupted fishing and related livelihoods in at least four provinces in central Vietnam, including Hà Tĩnh Province. Tourism was also severely impacted. The increased poverty that resulted affected more than 200,000 people. Locals took to the streets to demand action and compensation, with protests resulting in a government crackdown and the arrest of prominent protestors and journalists.
Eventually Formosa offered compensation, but later the same year (2016) was caught dumping around 260 tons of untreated dry waste at different spots in Hà Tĩnh Province. Cyanide was detected in some of the analysed samples of waste.
As pollution-related disasters – including those linked to climate change (itself in part a consequence of pollution) – become more frequent occurrences we can expect refugees from such catastrophes to be all the more numerous. People trafficking is likely to become yet more lucrative as demand for a better life somewhere else increases.
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