Category: PURE BLOG

The water source for Upper and Lower Heyford is a groundwater source drawn from Jurassic limestone aquifers, rather than a river or reservoir. In plain terms, rain falls on higher land, sinks through cracks, joints and porous layers in the rock, then moves through limestone beds until it reaches a spring, stream, or borehole. Thames Water tell us that we are part of their Deddington water supply zone, that this is borehole water that goes through Heyford Hill. They say that they THINK that the treatment works are valve-fed off Duns Tew. Despite two lengthy exchanges, they still refuse to provide any further detail, so far.

The local geology sits within the Middle Jurassic limestone and clay sequence of north Oxfordshire. The key rocks include Cornbrash, Forest Marble Formation, and White Limestone Formation, which form part of the wider Great Oolite Group. The Cornbrash is a rubbly, fossil-rich limestone with clay-rich partings, and it often sits above the Forest Marble Formation (British Geological Survey, n.d.-a). The Forest Marble is not just marble; it includes limestone, mudstone and clay-rich beds (British Geological Survey, n.d.-b). This mix matters because limestone can carry water, while clay-rich beds can slow or divert it.

The White Limestone Formation is especially important because it is classed locally as a “Principal Aquifer” and is used for local water supply in the Upper Heyford area (Cherwell District Council planning document, 2018). A principal aquifer is a rock unit that can store and yield enough water for public supply and can also feed rivers and wetlands. The British Geological Survey and Environment Agency classify aquifers in this way to show their value for drinking water and for the wider water system (British Geological Survey, n.d.-c).

Water in these limestone aquifers may move through pores in the rock, but also through fractures, joints and solution-widened cracks. This means flow can be uneven. In some places water may move quite slowly through fine pores; in others it may pass faster through cracks or weathered zones.

The British Geological Survey specifically notes that while the Great Oolite and Inferior Oolite aquifers are distinct, vertical leakage can occur where faults cut through lower-permeability layers (British Geological Survey, n.d.-d). In turn, this is particularly important near former air bases because pollution won’t always move as a neat plume. It can follow cracks, drains, made ground, ditches, old service trenches, and the line of least resistance.

For Upper and Lower Heyford then, the likely pattern is this: the former airfield sits on limestone and clay-rich Jurassic strata. Rainwater can wash contaminants from soil or made ground into shallow groundwater. Some water may perch above clay layers, while some may descend into limestone aquifers. Boreholes used for public supply may draw from deeper or more productive parts of the aquifer. Springs, brooks and drainage channels may also receive groundwater. This is why PFAS contamination at a former fire-training site raises concern: PFAS can dissolve in water, resist natural breakdown, and travel with groundwater.

This does not prove that a given tap supply is contaminated. It does mean the local geology creates plausible routes that should be mapped, tested and monitored. The key evidence that we need includes the borehole locations, depth, screened aquifer, source protection zone, groundwater flow direction, PFAS results in raw and treated water, and PFAS results in nearby surface water and sediments.

References

British Geological Survey. (n.d.-a). Cornbrash Formation. BGS Lexicon of Named Rock Units. https://webapps.bgs.ac.uk/lexicon/lexicon.cfm?pub=CB

British Geological Survey. (n.d.-b). Forest Marble Formation. BGS Lexicon of Named Rock Units. https://webapps.bgs.ac.uk/lexicon/lexicon.cfm?pub=FMB

British Geological Survey. (n.d.-c). Aquifer designation data. https://www.bgs.ac.uk/datasets/aquifer-designation-data/

British Geological Survey. (n.d.-d). Properties of the Great Oolite and Inferior Oolite aquifers. https://www2.bgs.ac.uk/groundwater/waterResources/thames/limestones.html

Cherwell District Council. (2018). Ground conditions and geology: Upper Heyford planning documentation. https://planningregister.cherwell.gov.uk/Document/Download?fileName=9192714.pdf&imageId=102&isPlan=False&module=PLA&planId=107372&recordNumber=66077

Not everyone will want to read this. It does get a bit detailed, however, if you are curious how these forever chemicals work, read on. References are provided at the end.

PFAS do not make a child, adult, or older person ill in a simple one-cause, one-disease way. They act more like persistent chemical stressors. Many PFAS bind to blood proteins, circulate through the body, pass through the liver and kidneys, and can remain in the body for months or years. This gives them repeated chances to disturb immune, endocrine, liver, kidney, placental, and metabolic systems. The final risk depends on the compound, dose, route, length of exposure, age, sex, genes, diet, poverty, stress, and other pollutants (ATSDR, 2024).

Child Health

In children, the clearest concern is immune function. PFAS exposure has been linked with lower antibody response to some vaccines. The National Academies judged decreased antibody response in children and adults to have sufficient evidence of association, although it noted that this does not prove higher infection rates or poorer vaccine effectiveness in every case (National Academies of Sciences, Engineering, and Medicine [NASEM], 2022). EFSA also treated reduced vaccine response as the critical effect when setting a tolerable weekly intake for four PFAS: PFOA, PFNA, PFOS, and PFHxS (EFSA CONTAM Panel, 2020). Mechanistically, PFAS may disturb immune-cell signalling, inflammatory control, oxidative stress, and nuclear receptor pathways. These processes help immune cells mature, communicate, and make antibodies.

Adverse pregnancy outcomes

PFAS can also matter before birth. The placenta controls oxygen, nutrients, hormones, immune tolerance, and waste exchange. Some PFAS cross the placenta and may disturb placental blood flow, oxidative stress, lipid signalling, and growth-related pathways. This gives a plausible route to the small reductions in fetal or infant growth seen in some studies. NASEM judged reduced birth weight to have sufficient evidence of association with PFAS exposure (NASEM, 2022).

Adult health

In adults, PFAS exposure appears most strongly linked with dyslipidaemia, or disordered blood lipids. NASEM judged the evidence sufficient for dyslipidaemia in both adults and children (NASEM, 2022). PFAS can affect liver pathways that regulate fatty-acid transport, bile acid handling, cholesterol clearance, and nuclear receptors such as PPARs. The result may be higher total or LDL cholesterol in some exposed people. This does not mean PFAS alone causes heart disease, but it may add to long-term vascular risk.

PFAS may also affect the liver, thyroid, kidney, and cancer risk. Reviews link some PFAS with altered immune and thyroid function, liver disease, lipid and insulin dysregulation, kidney disease, reproductive and developmental effects, and cancer, though much evidence still centres on older “legacy” PFAS such as PFOA and PFOS (Fenton et al., 2021). NASEM judged kidney cancer in adults to have sufficient evidence of increased risk, while thyroid disease, liver enzyme changes, breast cancer, testicular cancer, and ulcerative colitis sit in weaker evidence categories (NASEM, 2022).

Impacts on the elderly

In older people, PFAS may matter because ageing reduces reserve. Older adults may already have weaker immune response, poorer kidney function, higher cholesterol, thyroid disturbance, or multiple medicines that rely on liver and kidney clearance. PFAS may therefore push stressed systems closer to clinical illness. The core point is risk shift, not fixed fate. Across the life course, PFAS can nudge immune, endocrine, liver, kidney, placental, and lipid systems away from normal regulation. In one person, this may not prove cause. In a population with raised exposure, it can increase the burden of disease.

References

Generally, I rely on what are known as ‘meta analyses’ as they tend to be more reliable than individual pieces of research. I have also tried to make sure that these are accessible without going through a pay-wall – if you hit one, do get in touch and let me know before you spend any money.

Agency for Toxic Substances and Disease Registry. (2024). Health effects: PFAS information for clinicians. U.S. Department of Health and Human Services. https://www.atsdr.cdc.gov/pfas/hcp/clinical-overview/health-effects.html

EFSA CONTAM Panel. (2020). Risk to human health related to the presence of perfluoroalkyl substances in food. EFSA Journal, 18(9), Article e06223. https://doi.org/10.2903/j.efsa.2020.6223

Fenton, S. E., Ducatman, A., Boobis, A., DeWitt, J. C., Lau, C., Ng, C., Smith, J. S., & Roberts, S. M. (2021). Per- and polyfluoroalkyl substance toxicity and human health review: Current state of knowledge and strategies for informing future research. Environmental Toxicology and Chemistry, 40(3), 606–630. https://doi.org/10.1002/etc.4890

National Academies of Sciences, Engineering, and Medicine. (2022). Guidance on PFAS exposure, testing, and clinical follow-up. The National Academies Press. https://doi.org/10.17226/26156