Materia Oscura: Instrumentation Development to Observe the Invisible

This project aims to draw on an area of expertise supported by the STFC core science programme, ultra-precise radioactivity measurement and calorimetry developed for dark matter and neutrino physics, and develop application of these techniques to the problem of measuring lead contamination in water and food.

The motivation for growing capacity for and developing new lead measurement techniques is that lead pollution is the #1 cause of loss of life expectancy in the world, and currently 2 of the top 10 worst pollution problems in the world are associated with lead [PureEarth2016]. This is a problem both in LMICs and in high income countries- recent examples like the Flint, Michigan, USA, water safety breaches demonstrate that water quality in violation of WHO guidelines can happen anywhere, and information about water quality, and its variation in time, is not widespread. Even 'clean' techologies, like electric cars, employ traditional lead-based batteries; the disposal of these batteries is a leading contributor to lead pollution, particularly in LMICs.

The work in this proposal aims to make lead water contamination measurements accessible to anyone with a mobile phone. Currently, such measurements require expensive, specialized equipment or 6-month measurements to reach relevant sensitivity levels for human health- even 0.1 parts per million contamination with lead produces devastating biological impacts. Developing mobile-phone assay capability makes widely-distributed metrology and real-time, crowd-sourced monitoring possible, and therefore would have transformative impact on the public health problems associated with lead pollution.

While mobile-phone based radioassay has been prototyped for higher-energy and higher-rate radioactive decays, nothing exists currently to assay lead. Reaching the sensitivity levels required for lead is an incredibly challenging problem, which we propose to address by leveraging the precision calorimetry techniques in silicon (Si) detectors developed by the DAMIC and DMTPC dark matter experiments, together with the lead assay coincidence methodology developed by the DEAP-3600 dark matter experiment that gives a factor of up to 10,000 in background suppression beyond conventional techniques.

Our ultimate goal is to to develop a mobile phone application to measure the presence of lead in water samples. The app will employ the phone Si sensor (the camera) to perform radio-assay, with the goal of reaching the 10 parts per billion (ppb) sensitivity level, which is the World Health Organization limit on lead contamination in drinking water.

This proposal aims to develop pathways to translate the expertise in material radio-assay developed for particle astrophysics into impact on human health, through quantifying the incidence of a leading environmental toxin, lead. The ultimate goal is to reduce the health impacts of lead pollution. This project takes the approach that the first problem to address is to develop open source tools that can be widely applied to quantify the presence of lead, pursuing the idea that what can be measured can then be improved.

Lead exposure accounts for over 850,000 deaths each year due to long-term effects on health, with the highest burden in LMICs. The Institute for Health Metrics and Evaluation also estimates that lead exposure accounts for 9% of the global burden of idiopathic intellectual disability, 4% of the global burden of ischaemic hearth disease, and 7% of the global burden of stroke [ref: Institute for Health Metrics and Evaluation (IHME). GBD Compare.] Mexico is the world's 5th largest producer of lead and 40% of its production is used locally in different industrial processes that cause lead contamination of the environment.

This research proposal aims to deliver smart technology that can rapidly evaluate lead content in food and water using mobile instruments, eliminating the need for expensive and time consuming laboratory measurements and minimising health risks through immediate identification and alerts of toxicity. Measurements of Pb210 using the CMOS-based technology will be baselined against existing BEGe gamma spectroscopy detectors we have developed at Boulby. The Pb210 to total lead content will be correlated using our world-class ICP-MS facility. The UK BEGe and ICP-MS facilities, with the Mexico site coming online to allow local assays, will be used continuously to de-risk the technology development and perform Quality Control (QC) and Quality Assurance (QA) assessment of final products. Samples of, initially, water and coffee beans will be collected for assay from 50 sites identified across Mexico and Argentina where extensive quantitative peer-reviewed literature on lead-content from recent years is in place.

The impact of our sensitivity developed for rare-event physics searches extends beyond lead to all heavy metals. Our detection limits and control of systematics far exceeds that typical of facilities used to measure heavy metal toxicity in food and water from arsenic, cadmium, lead, copper, zinc, and TiO2 - which also represents risk due to its ubiquitous use yet poor control of nanoparticle content that cross blood-brain barriers. Arsenic in rice products is a particular concern due to identification of dangerously high levels in imported rice goods. LMICs such as Argentina, Brazil, China, and India, all leading rice exporters, have poor monitoring and controls for toxicity with the domestic population particularly vulnerable. We are developing calibration and analysis methods which can be adopted by virtually all similar laboratories to achieve comparable uncertainties. With up-skilling and training received by our project partners, this capability will be directly transferred to Argentina and Mexico.

The new low-background facility at Comarca Minera opens technical capabilities to provide services that lead to both greater economic output through QC of exported goods, and welfare through reduction in Disability-Adjusted-Life-Years. The establishment of such a low-background facility can derive impact beyond lead and heavy metal toxicity. Assay capability that can identify low levels of U238, Th232, and other radioisotopes is of interest to commercial and industrial companies. The new facility in Mexico would benefit from our partnerships and experience in industrial engagement to rapidly establish their own programme in support of local and national manufacturing, and to facilitate entirely new opportunities spawned by the presence of new technical capability.