Blue water is sourced from rivers, lakes, and reservoirs and is used for drinking water, growing crops, and food production(1). Approximately 75% of blue water use (BWU) comes from food systems(2). Dietary change is necessary to meet net zero BWU sustainability goals by 2050(3). While there is some information on diet-associated BWU for the Republic of Ireland (ROI)(4), BWU across the Island of Ireland is unknown. This study aimed to quantify the environmental impact of BWU of daily diets across adults aged 18-64 on the Island of Ireland, to determine population characteristics, nutrient intakes and key food sources influencing emissions.
The Northern Ireland sub cohort of the UK National Dietary Nutrition Survey (2016-
2019)(5) and the Irish National Adult Nutrition Survey (2008-2010)(6) were analysed. Information on food and nutrient intakes was extracted from four-day food diaries for a total of 1,484 adults aged 18-64 years. BWU values were assigned for each food(7) and the population was grouped into tertiles of low (T1), medium (T2), and high (T3) BWU. Differences in population characteristics, key nutrients (%TE or per 10MJ) and contributing food sources were examined across these tertiles. Statistical analysis was performed using chi-square and one-way ANOVA with covariates (age, BMI, Sex, Survey type and social class) and correcting for multiple comparisons as appropriate (P<0.001).
BWU for the Island of Ireland was 481.9 ± 440.4 L/day, 524.7 ± 448.0 L/day for Northern Ireland and 474.9 ± 438.6 L/day for the ROI and 100% of the population did not exceed the BWU planetary boundary of ≤786 L/day(8). Males had a higher contribution to the total BWU than females on the Island of Ireland (513.3 ± 482.2 L/day vs 453.2 ± 385.8 L/day). ‘Tea, coffee and water’ (76%), ‘rice and rice dishes’ (4%) and ‘fruit and fruit juice’ (2.5%) were the
greatest contributors to BWU. When tertile analysis was performed, BWU from ‘tea, coffee and water’ was significantly higher for T3 at 837 ± 468.8 L/day versus T1 (57 ± 50.9 L/Day), this was similar for ‘rice and rice dishes’, where BWU in T3 was 26.3 ± 44.0 L/Day versus T1 (13.3 ± 25.2 L/Day). When nutritional analysis was performed, differences (P<0.001) across tertiles of BWU were observed for energy (11% increase between tertile 1 and 3), magnesium (12% increase across tertiles) and potassium (8% increase across tertiles).
Overall, a shift to more sustainable diets is needed to prevent BWU boundaries being exceeded in the future. By filling a literature gap on the environmental impact of the Northern Irish diet, this study complements previous research on the ROI, offering a comprehensive view of the BWU footprint and providing a basis for the development of strategies to improve diet-related BWU on the Island of Ireland.
References
Rost, S. et al. (2008) ‘Agricultural Green and blue water consumption and its influence on the Global Water System’, Water Resources Research, 44(9). doi:10.1029/2007wr006331.
de Fraiture, C. and Wichelns, D. (2010) Agricultural Water Management, 97(4), pp. 502–511. doi:10.1016/j.agwat.2009.08.008.
Pye, S. et al. (2017) Nature Energy, 2(3). doi:10.1038/nenergy.2017.24
Kirwan, L.B. et al. (2023) Nutrients, 15(4), p. 981. doi:10.3390/nu15040981.
Public Health England (2020). NDNS: results from years 9 to 11 (2016 to 2017 and 2018 to 2019). [online] GOV.UK. Available at: https://www.gov.uk/government/statistics/ndns- results-from-years-9-to-11-2016-to-2017-and-2018-to-2019.
Irish Universities Nutrition Alliance (2011) The National Adult Nutrition Survey. http://www.iuna.net/
Scheelbeek, P. et al. (2020) , BMJ Open, 10(8). doi:10.1136/bmjopen-2020-037554.
Chaudhary, A. and Krishna, V. (2021) One Earth, 4(4), pp. 531–544. doi:10.1016/j.oneear.2021.03.006.

Blue water is sourced from rivers, lakes, and reservoirs and is used for drinking water, growing crops, and food production(1). Approximately 75% of blue water use (BWU) comes from food systems(2). Dietary change is necessary to meet net zero BWU sustainability goals by 2050(3). While there is some information on diet-associated BWU for the Republic of Ireland (ROI)(4), BWU across the Island of Ireland is unknown. This study aimed to quantify the environmental impact of BWU of daily diets across adults aged 18-64 on the Island of Ireland, to determine population characteristics, nutrient intakes and key food sources influencing emissions.
The Northern Ireland sub cohort of the UK National Dietary Nutrition Survey (2016-
2019)(5) and the Irish National Adult Nutrition Survey (2008-2010)(6) were analysed. Information on food and nutrient intakes was extracted from four-day food diaries for a total of 1,484 adults aged 18-64 years. BWU values were assigned for each food(7) and the population was grouped into tertiles of low (T1), medium (T2), and high (T3) BWU. Differences in population characteristics, key nutrients (%TE or per 10MJ) and contributing food sources were examined across these tertiles. Statistical analysis was performed using chi-square and one-way ANOVA with covariates (age, BMI, Sex, Survey type and social class) and correcting for multiple comparisons as appropriate (P<0.001).
BWU for the Island of Ireland was 481.9 ± 440.4 L/day, 524.7 ± 448.0 L/day for Northern Ireland and 474.9 ± 438.6 L/day for the ROI and 100% of the population did not exceed the BWU planetary boundary of ≤786 L/day(8). Males had a higher contribution to the total BWU than females on the Island of Ireland (513.3 ± 482.2 L/day vs 453.2 ± 385.8 L/day). ‘Tea, coffee and water’ (76%), ‘rice and rice dishes’ (4%) and ‘fruit and fruit juice’ (2.5%) were the
greatest contributors to BWU. When tertile analysis was performed, BWU from ‘tea, coffee and water’ was significantly higher for T3 at 837 ± 468.8 L/day versus T1 (57 ± 50.9 L/Day), this was similar for ‘rice and rice dishes’, where BWU in T3 was 26.3 ± 44.0 L/Day versus T1 (13.3 ± 25.2 L/Day). When nutritional analysis was performed, differences (P<0.001) across tertiles of BWU were observed for energy (11% increase between tertile 1 and 3), magnesium (12% increase across tertiles) and potassium (8% increase across tertiles).
Overall, a shift to more sustainable diets is needed to prevent BWU boundaries being exceeded in the future. By filling a literature gap on the environmental impact of the Northern Irish diet, this study complements previous research on the ROI, offering a comprehensive view of the BWU footprint and providing a basis for the development of strategies to improve diet-related BWU on the Island of Ireland.
**References**
1. Rost, S. _et al._ (2008) ‘Agricultural Green and blue water consumption and its influence on the Global Water System’, _Water Resources Research_, 44(9). doi:10.1029/2007wr006331.
2. de Fraiture, C. and Wichelns, D. (2010) _Agricultural Water Management_, 97(4), pp. 502–511. doi:10.1016/j.agwat.2009.08.008.
3. Pye, S. _et al._ (2017) _Nature Energy_, 2(3). doi:10.1038/nenergy.2017.24
4. Kirwan, L.B. _et al. _(2023) _Nutrients_, 15(4), p. 981. doi:10.3390/nu15040981.
5. Public Health England (2020). _NDNS: results from years 9 to 11 (2016 to 2017 and 2018 to 2019)_. [online] GOV.UK. Available at: https://www.gov.uk/government/statistics/ndns- results-from-years-9-to-11-2016-to-2017-and-2018-to-2019.
6. Irish Universities Nutrition Alliance (2011) The National Adult Nutrition Survey. http://www.iuna.net/
7. Scheelbeek, P. _et al. _(2020) , _BMJ Open_, 10(8). doi:10.1136/bmjopen-2020-037554.
8. Chaudhary, A. and Krishna, V. (2021) _One Earth_, 4(4), pp. 531–544. doi:10.1016/j.oneear.2021.03.006.

OC43 - Environmental impact of blue water use by adults aged 18-64 on the Island of Ireland

Unique to the new Congress (previously the Summer Conference) is that you will have greater opportunity to engage with more nutrition science than ever before. In 2024 the core programme will be delivered by the Irish Section of The Nutrition Society, supported by the Science Committee. The theme of these symposia will be ‘new data – focused approaches and challenges’. Outside of the core programme you will have the chance to hear the latest research from the Society’s partner organisations, universities, the private sector and more, on a diverse range of research.