• Dr. Anusha Seneviratne

How much does Human Welfare depend on Nature? | Part 1: Polluting the Planet

Updated: Jul 28, 2021

As I read about the environmental destruction carried out by multi-national corporations clearing land to grow palm oil, sugar cane and other crops in the book "Landgrabbers" by Fred Pearce, I learned how we are producing foodstuffs and other materials at an unnecessarily large scale to satisfy a human population accustomed to consumerism. While poorer populations who lived in harmony with nature for thousands of years, have their human rights neglected and even lose their lives. Consumerism is driving behaviour that eventually harms the long-term health and welfare of humanity. Increasing urbanisation and economic development means our lives are more absorbed with gaining wealth, keeping with the latest trends and a throwaway culture. In addition, the growing human population is increasing competition for limited resources, which unfortunately is manipulated to fuel xenophobia in many countries. I thought the "People's Manifesto for Wildlife" initiated by Chris Packham in 2018 could be strengthened by including a Ministry for the environment and human health. As I searched online for existing policies, the most common policy area I encountered was the effect of climate change on human health and how to develop more resilient health systems. It seems not many were making the connection that many causes of environmental damage, climate change and the ecological crisis, are also causes of many human diseases, and have detrimental effects on our quality of life. It is only in the last few years that health policy experts introduced the concept of ‘Planetary Health’, defined as “the health of human civilisation and the state of the natural systems on which it depends” [1,2]. While awareness of Earth's dire situation has seen a significant boost since late 2018, making necessary changes happen fast enough is proving a challenge with the recent surge of right-wing anti-environmentalism reaching powerful positions in the form of the previous US and current Brazilian Presidents for example. We have a lot of work to do in very little time. We can make an enormous impact by discouraging consumerism and developing existing technologies to cut carbon emissions. Many believe meaningful change means a poorer quality of life, which has some truth as developed countries are responsible for far more carbon emissions than developing nations. But is that a reasonable association to make? Some indulgences must be stopped but is that so bad for our welfare? I hope my next four blog posts will offer a different perspective and a deeper understanding of how we depend on the natural world to survive, and why we need to save it fast. In this series, I will examine how solutions for our planetary crisis will benefit our quality of life and health. And how it won't necessarily come with the cost of living poorer lives. I will explore the common causes of non-communicable diseases and loss of land for nature, and why thriving natural ecosystems are essential for our well-being. But first, I will look at some of the sources of pollution that are damaging our ecosystems and our health.

Air Pollution  Carbon emissions have been rising exponentially since the industrial revolution. In percentage terms carbon dioxide (CO2) levels in our atmosphere are negligible compared to oxygen, at only 0.0391% currently. In absolute terms, atmospheric CO2 has fluctuated between 200 and 280 ppm (parts per million) for the last 400,000 years. Now it consistently tops 400ppm, which is 50% greater than before the industrial revolution [3]. The numbers may seem negligible, but the effect on our climate is not. Global temperatures have increased by approximately 1.2°C over the last century [4], and the trend does not match solar activity [5]. This may not seem like much, but it is already having devastating consequences on our climate and could lead to a slippery slope of unknown magnitude. For instance, wildfires are a normal part of the annual cycle, when burnt vegetation renews soils leading to new growth following rainfall. In today's changing climate, wildfires are occurring where they have never occurred before, like parts of the U.K. and the Arctic. Most worryingly wildfires are burning through natural carbon sinks, such as underlying peatlands, releasing enormous amounts of CO2. Our oceans have absorbed one third of carbon emissions, with plankton and coral converting carbon into carbonates. But with rising emissions and ocean acidification, this process will become less efficient. We are already witnessing large-scale coral bleaching events for instance.

NASA Graphic: The relentless rise of carbon dioxide (

Pollutants can directly affect our body functions, even when we don't feel any symptoms. It is well documented that air pollution, particularly in heavily polluted cities and when exacerbated by hot weather, can cause or worsen lung disease as pollutants trigger immune responses that typically fight infection or cause an intense allergic response. A long-term study in six US cities showed air pollutants, in particular ozone (O3) exacerbates the progression of emphysema [6]. Patients already suffering from lung diseases were more prone to infection when exposed to pollution as their immune defences were compromised. Exposure to particulates less than 2.5 microns in size (PM2.5 - the most dangerous pollutant as they are small enough to penetrate our airways and other tissues), diesel exhaust particles and cigarette smoke stimulated the same inflammatory signalling pathways and immune cells that are normally at the front line in fighting infection [7]. Thus, being constantly exposed to pollutants could lead to chronic inflammation in the body, increasing the risk of chronic diseases like diabetes and heart disease [8]. In fact, the hearts of individuals exposed to PM2.5 in London had changes such as enlargement comparable to the early stages of heart failure [9]. Air pollution is positively associated with mortality from COVID-19 [32], and unfortunately this pandemic has demonstrated that the poorest in society are worst hit by pollution and these health burdens. It's not just our immune systems that are under assault from pollution. Urban birds elevate their expression of inflammatory and anti-oxidative genes suggesting they may be battling more infections than rural birds, or their immune systems are directly stimulated by pollutants. Chicks fledging from urban nests had shorter telomeres on their cellular chromosomes than those of fledging forest chicks, an indication of stress and reduced future lifespan. Chicks with the shortest telomeres died before reaching adulthood. However urban great tits that survived to adulthood were stronger than the average forest adult [10]. Urban blue tits had higher polyunsaturated fatty acids than rural birds, which can increase inflammatory responses. Urban Sparrows show a higher level of lipid peroxidation compared to their rural counterparts [11]. Some studies show that flowers grown in urban environments have lost their scent due to pollution [12], thus it is more challenging for pollinators to find flowers as they partly rely on scent. Cities are believed to be oases for many species of wildlife as highlighted by London being named the world's first national park city. But if we don't curb carbon emissions and other air pollutants soon, biodiversity in urban environments may not last long.

Plastics    As you will be aware, the build-up of plastics in our environment is a major concern, particularly due to the damage caused to marine life. In spite of our efforts to recycle as much plastic as possible, it seems even plastics we submit for recycling is actually shipped to developing countries only to be dumped on land where it leaches into rivers and eventually into our oceans [13]. What is probably of greatest concern is the shedding of microplastics - micrometre sized particles shed from larger pieces of plastic, entering organisms as small as plankton and thus our food chain. Microplastics can be shed from packaging and plastic objects dumped on landfill sites, beaches and in waterways. ‘Animal Babies’ on the BBC in 2019 showed how the seabed off the Californian coast near a golf course, is littered with golf balls shedding their outer plastic layer generating microplastics [14]. These golf balls were even being retrieved by baby sea otters looking for food. As fish consume plankton, and are eaten by larger fish or marine creatures, microplastics accumulate in larger creatures further up the food chain. And we consume many of these fish.

Wildlife consuming plastic in the oceans is a major problem. (Photo credit: Ingrid Taylar, Flickr, Stop Trashing my Ocean).

Research shows exposure to microplastics reduces the efficacy of mussels' digestive processes, causes hepatic stress in European Sea Bass, dysregulates antibody production and immune function in juvenile Salmon [15], and causes bleaching and tissue necrosis of stony corals [16]. Organisms like Mussels and Oysters can filter litres of polluted water a day, thus disruption to their digestive systems would damage our battle against polluted seas. As larger marine creatures - like whales, sea turtles and seabirds - consume plastic, they feel full, do not feed sufficiently and starve to death. Often these plastics are contaminated with chemicals or microbes that disrupt gut microflora and immune function [17]. These affects can be further magnified in our bodies as we consume the affected fish, mussels and other seafood. Microplastic particles have even been found in sea salt produced for human consumption [18]. On the BBC's ‘War on Plastic’ series in 2019, we were shown how piles of plastic are burned in countries receiving our ‘recycled’ plastics such as Malaysia, releasing toxic gases like Dioxins, Furans, Mercury and Polychlorinated Biphenyls [19]. The released chemicals and gases include carcinogens, disruptors of thyroid and reproductive systems, can elevate risk of heart disease, aggravate respiratory issues such as asthma and emphysema. Local children suffer breathing problems and nosebleeds. Closer to home, microplastic fibres shed from synthetic clothing into the air can be small enough to penetrate deep into the alveoli of our lungs. These microfibres can also carry infections and other pollutants, persist for long periods due to their durability and become carcinogenic [20]. Worryingly microplastics have been found in the remotest parts of the Arctic, in fact 17 types ranging from those derived from packaging to fishing nets, possibly due to global shipping and tourism [21]. Ocean currents exacerbated by climate change are making accumulation of plastics and microplastics in ocean hotspots even worse. This makes the consumption of microplastics by small organisms such as plankton even more likely. It is highly concerning as we depend on phytoplankton to photosynthesise and produce 50% of our atmospheric oxygen. Phytoplankton also have a direct effect on our weather by producing dimethyl sulphide, which undergoes chemical transformations in the air to eventually seed droplets to form clouds [22]. Plastic is produced by companies like Ineos in Scotland who ship large amounts of shale gas from the US and burn it with oil to produce plastic pellets. The amount of fossil fuel burned is equivalent to the fuel used by three Scottish cities combined [13]. While it is a significant challenge to clear our oceans of plastic, we must urgently find alternative materials to replace single-use plastic that are either recyclable, biodegradable or compostable and where the breakdown products would benefit our environment. A promising example is a polythene packaging like substance derived from Seaweed, as shown on the BBC's ‘Drowning in Plastic’ in 2018. This substance dissolves on contact with water, thus is biodegradable. Seaweed farming could have the added benefit of being a carbon sink as it has been estimated that covering just 9% of the world's ocean surface could restore atmospheric CO2 to pre-industrial levels [23] although it's not known if it could deprive local marine life of oxygen or release ozone-destroying chemicals. But a material like this will not be practical in every situation, hence the need for a variety of alternatives. As a laboratory scientist, I often despair at the amount of plastic we dispose of, from pipette tips to cell culture flasks. Due to the need for sterility and enzyme-free materials, and the level of contamination in used plastics consumables, laboratory and clinical waste cannot enter the normal waste or recycling streams and must be incinerated. But as described above, this releases harmful microplastics, toxic gases and adds to carbon emissions. Incineration is necessary for clinical waste to prevent the spread of infection but if a more easily degradable substance can be used to manufacture lab and clinical consumables, that would also not produce harmful waste pollutants, it would be hugely beneficial for our environment.

Medicine The interaction between medicine and the environment can be looked at in two ways. Firstly, we rely on the natural world to provide many of our medicines. Secondly, manufacture and consumption of these medicines can affect the environment. The list of medicines we obtain from the natural world is endless. Metformin, used to control blood sugar levels in type 2 diabetics with beneficial cardiovascular effects, is extracted from the French Lilac plant. Digoxin, which is used to treat cardiac arrhythmias and increase the force of heart contractions in patients with severe heart failure, is extracted from Foxgloves. The precursor compound of the painkiller and anti-coagulant Aspirin is extracted from the leaves of Willow trees. The cholesterol-lowering drug Lovastatin is naturally found in Oyster mushrooms. These are just a few examples of how we depend on nature for medicine.

More recently pharmaceuticals have been developing synthetic compounds, but even these are modified versions of compounds extracted from plants. Examples include Paclitaxel, used to treat various types of cancer, which was initially isolated from Pacific and European Yew trees [24]. Hundreds of medicinal compounds have been discovered in our forests, and with the loss of so much of our native forests, there may be many more compounds that remain undiscovered. Therefore, we must protect what remains and re-wild unused land to preserve and restore biodiversity, to maintain access to medicinal compounds while also ensuring we do not destroy natural ecosystems in the harvesting process.

It is not just plants that are saving our lives. Many antibiotics were first isolated from soil bacteria. In the battle against antibiotic resistance, a new antibiotic termed Teixobactin, isolated from a bacteria that can only grow in soil and not traditional lab culture conditions, was found to target Gram positive bacteria including resistant strains like MRSA and Tuberculosis [25].

Medical waste, like this truckload being dumped in Peru, presents a challenge to the environment. (AveryAudio from Wikimedia).

With the production of medicines also comes the responsibility of what impact the waste products have on the environment. Numerous medicinal compounds such as antidepressants, Ibuprofen, Paracetamol, Beta-blockers and antibiotics have been found in drinking water and soil [26]. While the majority of medical waste is incinerated as previously mentioned, 30-90% of drugs are excreted as the active substance in the patient's urine and from livestock animals. There is also the problem of dumping of medical waste on unused land and waterways, and incorrect disposal of unused or expired medication down sinks and toilets [27]. While returning unused medication to pharmacies is encouraged, this does not happen for 50-90% of unused medication in EU member states. The discharge volume of antibiotics into wastewater from European hospitals is estimated to be 86 tonnes a year [28]. This raises the risk of multi-drug resistant infections thriving in the environment. Current wastewater treatments cannot guarantee removal of all medicinal products and their efficacy depends on the technology used, the chemical nature and concentration of the product present. There is some evidence showing landfills accepting sewage sludge can leach medicinal products at higher concentrations than wastewater treatment plants. Extreme weather events can increase the risk of sewage leaks or overflows which can impede the treatment of wastewater. Other organisms can suffer biotoxicity from antibiotics, anti-cancer drugs and fungicides, which are developed to be lethal to their target organism. A well-documented example is when vultures feeding on livestock carcasses in the Indian sub-continent died of kidney failure as the carcasses contained Diclofenac - a potent anti-inflammatory painkiller given to livestock to fend off various diseases [29,30]. Diclofenac is so potent that a 10-tablet blister of a typical 50mg dose can pollute up to 5 million litres of water. Vulture populations plummeted by 99% and veterinary Diclofenac was subsequently banned in India. There is a danger that other lipid-soluble medicinal products could bioaccumulate in animal fat tissues leading to biotoxicity, particularly in predators towards the top of the food chain. Antidepressants can impair the reproduction of fish. The beta-blocker Propanolol is 100 times more toxic to algae than humans even though its target adrenergic receptor is not present in plants [31]. These medicines are meant for our consumption, but constant exposure to these molecules, especially for healthy individuals, can have harmful effects in the long-term. Constant exposure to anti-bacterial and anti-viral compounds can increase resistance in human gut flora reducing future efficacy of these products. It is not believed to pose an immediate risk, but exposure to insecticides via consumption of fruit and vegetables, and medicinal products in drinking water could bioaccumulate over time. It is difficult to establish a safe limit for these substances, especially for children for whom the cumulative effect maybe worse. Over-prescription of medicines like antibiotics is also a concern for human and environmental health. There is some debate over the efficacy of incineration of medical waste as tests show it does not modify the mutagenic and genotoxic properties of anti-cancer medicines. It is also very difficult to detect medicinal products persisting in the environment due to limitations in analytical methods [27]. The EU has numerous directives in place to limit the impact of medicinal products on the environment. As the UK has left the European Union, it is essential such legislation remains in place and is strengthened to limit the environmental impact of human and veterinary medicine. Currently manufacturers of medicinal products in the EU must obtain Marketing Authorisation (MA) from the EU first. This application includes an Environmental Risk Assessment (ERA) for the active ingredient only, although not for all medicines or other products such as vitamins, peptides, vaccines and herbal products. The risk/benefit analysis includes environmental risks for veterinary products but not for human medicinal products [27]. Sometimes the hazard is difficult to assess, therefore it is not possible to carry out a full risk assessment. In general, no environmental risk assessment is required for new drug applications in the EU or the US. Given the risk to both environmental integrity and human health as detailed above, the process for obtaining an MA should include an ERA for all ingredients of human medicines. In part 2, read how food and substances we indulge in a little too much, can damage our health and the environment. This blog post is updated from the original version published on in 2019.


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