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UN Global Goal 3 & The Tryptophan Breakthrough

UN Global Goal 3 (SDG 3 or Global Goal 3) concerns itself with basic human health, and Chelsea's Tryptophan sensors have a key role to play in this. In the fine words of the UN declaration, ‘By 2030, substantially reduce the number of deaths and illnesses from hazardous chemicals and air, water and soil pollution and contamination.’

What is UN Sustainable Development Goal 3?

UN Global Goal 3

In the fine words of the UN declaration, ‘By 2030, substantially reduce the number of deaths and illnesses from hazardous chemicals and air, water and soil pollution and contamination.’ Inadequate and unsafe drinking water, sanitation and hygiene is linked to 60 per cent of the disease burden from diarrhoea. UN Goal 3 is one of 17 Sustainable Development Goals established by the United Nations General Assembly in 2015. UN Global Goal 3 (SDG 3 or Global Goal 3) concerns itself with basic human health.

Tragically, the world is falling short on its promise of universal health coverage by 2030 and achieving universal health coverage remains a global challenge. The number of people incurring large out-of-pocket health expenses has been increasing and will likely continue to increase. Globally, the proportion of the population spending more than 10 per cent of their household budgets to pay for health services rose from 9.4 per cent to 12.7 per cent (927 million people) between 2000 and 2015. It is estimated that nearly 90 million people were pushed into extreme poverty by out-of-pocket health payments in 2015. An estimated 1 billion people will spend at least 10 per cent of their household budgets on health care in 2020, the majority in lower-middle-income countries. The income loss due to COVID-19 lockdown measures will likely exacerbate the situation.

Globally, two billion people consume water contaminated with faeces. This exposure increases the incidence of infectious disease such as diarrhoea, which alone results in more than half a million deaths per year in low- and middle-income countries. The most at-risk age group is children under five, with diarrhoea the second leading cause of death. In higher-income countries, risks remain due to the consumption of undertreated water from private supplies, or in public supplies, from failures in either water treatment or the integrity of the distribution network.

Diarrhoeal disease & UN Global Goal 3

Diarrhoeal disease is the second leading cause of death in children under five years old and is on its own responsible for killing a staggering 525,000 children every year. Diarrhoea can last several days and can leave the body without the water and salts that are necessary for survival. In the past, for most people, severe dehydration and fluid loss were the main causes of diarrhoea deaths. Now, other causes such as septic bacterial infections are likely to account for an increasing proportion of all diarrhoea-associated deaths. Children who are malnourished or have impaired immunity as well as people living with HIV are most at risk of life-threatening diarrhoea.

  • Diarrhoeal disease is the second leading cause of death in children under five years old. It is both preventable and treatable.
  • Each year diarrhoea kills around 525,000 children under five.
  • A significant proportion of diarrhoeal disease can be prevented through safe drinking-water and adequate sanitation and hygiene.
  • Globally, there are nearly 1.7 billion cases of childhood diarrhoeal disease every year.
  • Diarrhoea is a leading cause of malnutrition in children under five years old.

UN Sustainable Development Goal 3: “By 2030, substantially reduce the number of deaths and illnesses from hazardous chemicals and air, water and soil pollution and contamination”

One of the most significant interventions to prevent diarrhoea is safe drinking-water. Indeed, the World Health Organisation tasks member states and other partners to:

  • Promote national policies and investments that support case management of diarrhoea and its complications as well as increasing access to safe drinking-water and sanitation in developing countries;
  • Conduct research to develop and test new diarrhoea prevention and control strategies in this area;
  • Build capacity in implementing preventive interventions, including sanitation, source water improvements, and household water treatment and safe storage;
  • Develop new health interventions, such as the rotavirus immunization; and
  • Help to train health workers, especially at community level.

The tryptophan breakthrough

Traditionally, faecal contamination in drinking water is detected using faecal indicator organisms (FIOs), such as E. coli. This approach requires working with sterile equipment and reagents. Testing can take up to a day to return results due to the necessity of culturing. However, in lower- and middle-income countries, these requirements can restrict water-quality monitoring. Delays resulting from FIO methods also limit the ability to rapidly communicate the risks to local communities. As a result, UNICEF and the World Health Organisation (WHO) are looking for new technologies for the rapid detection of E. coli.

“… portable tryptophan-like fluorescence (TLF) sensors provide an easy-to-use method that is a more resilient indicator of the risk of faecal contamination to water supplies than thermotolerant coliform bacteria, known as TTCs, which have been the most common standard approach to water testing for decades”

Recent sensor research has focused on on-site testing using portable tryptophan-like fluorescence (TLF) sensors that require no reagents and provide instantaneous readings. While not a substitute for standard culturing methods, Chelsea technologies’ TLF sensors have the potential to be used for real-time microbial risk screening of drinking water supplies. Our sensors measure the fluorescence that is associated with the amino acid tryptophan, termed TLF. A measurement is obtained by either submerging a sensor in a water sample or using a small sample container that fits into the sensor, with results available in 60 seconds. A flow-through cell is used for online applications and all approaches require no reagents or other consumables.

The recent study led by James Sorensen of the British Geological Survey (BGS) using Chelsea Technologies’ Tryptophan sensors show how our technique exploiting the fluorescent properties of microbiological materials in water provides an easy-to-use method that is a more resilient indicator of the risk of faecal contamination to water supplies than thermotolerant coliform bacteria, known as TTCs, which have been the most common standard approach to water testing for decades. This makes UN Sustainable Development Goal 3 immediately more attainable, for in order to improve, you must measure first.

  ‘In situ fluorescence spectroscopy provides an instantaneous assessment of faecal contamination allowing rapid feedback to consumers to reduce their exposure to faecally contaminated drinking water. For example, in the UK, online fluorescence could minimise widespread boil alerts currently triggered when contaminated water is circulated and, potentially, consumed by thousands of people before there is any indication of contamination using standard approaches.’

Lead author James Sorensen, BGS

‘The ability to test in situ fluorescence as an indicator of faecal contamination risk in a wide range of environments and conditions has greatly improved both the evidence base for this method of water quality monitoring and our understanding of what fluorescence observed in water means.’

Co-author Prof Richard Taylor, UCL Geography

‘This robust, rapid method of monitoring the risk posed by faecal contamination has enormous implications in Uganda, not only for untreated water sources such as wells and springs, as it enables communities to respond rapidly to contamination events, but also for low-cost, continuous monitoring of piped water supplies.’

Co-author Dr Robinah Kulabako, Makerere University

The research, conducted by a collaborative team from the BGS, Makerere University in Uganda and UCL, examined changes in water quality over a 14-month period from 40 sources supplied by groundwater in the rapidly expanding town of Lukaya in southern Uganda. In this paper, Sorensen demonstrates that in-situ fluorescence spectroscopy is a more rapid and resilient indicator of faecal contamination risk in drinking water than faecal indicator organisms.

Chelsea Technologies’ UviLux tryptophan sensor

UViLux tryptophan sensor

The Chelsea Technologies’ UV UviLux Tryptophan Sensor fluorometer is designed for sewage detection through detection of aromatic hydrocarbons (PAH), CDOM, Tryptophan-like fluorescence (TLF), BOD or Optical Brighteners. The compact and highly sensitive fluorometers have excellent turbidity rejection and high ambient light rejection, making them suitable for use in water and wastewater treatment works, as well as natural waters at the surface and to depths of up to 1000 m.

Laboratory studies have clearly identified that TLF is produced by all bacteria tested, both laboratory and environmental freshwater derived; tryptophan is an essential amino acid produced by all living things. While this work has demonstrated very strong significant correlations between single species enumeration and TLF intensity, the omnipresence of TLF prevents it from being applied as a species-specific enumerator, for example as an E. coli counter. This is particularly problematic in complex surface waters where the microbial communities are diverse and complex, further complicated by optical interferences such as absorbance and turbidity.

Recently, the scientific literature has been moving away from the comparison of TLF to current water quality monitoring parameters and has focussed on exploring the benefit of this phenomenon as an informative parameter in its own right. This has been aided by the understanding that correction for optical inferences, such as turbidity and absorbance, can improve the robustness of the data generated. Informed by the scientific research, Tryptophan fluorometry sensors have been developed by Chelsea Technologies, reporting semi-quantitative corrected data. This allows for the comparison of different water bodies and sensors, enhancing the usefulness and robusticity of the data obtained.

 

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