Buying a Mine Means Buying Its Exposure History: The Human Capital Liability Missing from the Data Room

Every acquisition of an operating mine comes with two sets of books. The first sits in the data room: reserves, plant, permits and the safety record. The second is carried in the lungs, ears and medical files of the people who work there, and of those who have left. A share purchase transfers both, because the company that employed the workforce comes with the deal. An asset purchase can leave some liabilities behind, but in South Africa the workforce usually moves with the business, and who carries claims for past exposure then depends on the sale agreement and the statute.

Human capital is the asset a mine can least afford to lose, and it is where the longest-tailed liability in a transaction tends to hide. Disease from dust, diesel exhaust and radiation can take a decade or more to appear, long after the warranties have expired and the escrow has been released. In one South African gold mining cohort, more than half of silicosis cases first appeared on X-ray only after exposure had ended. Noise-induced hearing loss builds earlier, but it is permanent and often sits unanalysed in audiometry records.

01Why the liability stays hidden

The first reason is biology. Chronic silicosis usually takes at least ten years from first exposure to develop, and asbestos-related mesothelioma typically 30 to 40 years. Noise-induced hearing loss builds fastest in the first 10 to 15 years of exposure and is permanent, and the evidence does not show it progressing once exposure stops, so much of that liability can be measured at the deal date from existing audiometry. In a South African cohort of 2,235 gold miners, 14% developed silicosis, and in 57% of those cases the X-ray signs appeared only after exposure had ended, on average 7.4 years after leaving. A workforce can look healthy on the day of the deal.

The second reason is what the data room measures. Deal teams receive injury rates and incident logs, which measure safety events. The US Bureau of Labor Statistics notes that long-latency illnesses are difficult to associate with the workplace and are not adequately recognised and reported. In Great Britain about 11,000 deaths a year from occupational lung disease are linked to past exposure at work, against 126 workers killed in work-related accidents in 2025/26.

The third reason is the record itself. Exposure evidence on existing mines is often thin: area readings instead of personal samples, results never interpreted against a limit, surveillance never linked to exposure. It is thinnest where buyers look least: contractors the mine never measured, former employees on no surveillance list, sites on care and maintenance whose records have dispersed, and assets sold out of liquidation.

A survey existing is not the same as evidence existing. Our companion article sets out where exposure evidence fails under scrutiny: srghygiene.com/knowledge/exposure-evidence-eight-places-it-fails. In a transaction the buyer is relying on evidence someone else created, for purposes unrelated to the deal.

02Where the money goes

Southern Africa has seen what a mature occupational disease liability looks like. In 2011 South Africa's Constitutional Court held that the bar on common-law claims in the Compensation for Occupational Injuries and Diseases Act does not apply to mineworkers who qualify for compensation under the Occupational Diseases in Mines and Works Act, so they may sue a negligent employer for occupational lung disease. A silicosis and tuberculosis class action by gold mineworkers followed. In 2018 six companies agreed a settlement of about R5 billion, approved by the High Court in 2019, for workers at qualifying gold mines employed between 12 March 1965 and 10 December 2019 and their dependants. The Tshiamiso Trust administers it on top of statutory compensation. By 25 September 2026 the Trust reported R2.81 billion paid on 28,802 claims, with 165,339 lodged and lodgements open until 10 December 2029.

That liability crossed borders. The Trust serves former gold mineworkers in South Africa, Lesotho, Eswatini, Mozambique, Zimbabwe, Botswana and Malawi. By 25 September 2026 its progress report showed R219.3 million paid on 2,050 claims from Botswana, with 6,081 lodged. The former workforce is part of the liability. In the United States, coal bankruptcies between 2014 and 2016 moved an estimated US$865 million of black lung benefit responsibility to a federal trust fund. Experienced parties allocate this liability explicitly in the sale agreement, for example by leaving obligations to former employees with the seller.

In Botswana, the Workers' Compensation Act (Cap 47:03) makes employers liable for scheduled diseases including silicosis, silicotuberculosis and noise-induced hearing impairment. Liability falls on the last employer in the prescribed period unless it proves otherwise, disease is presumed to arise from work in a prescribed occupation, and section 41 preserves civil claims where the injury or disease arose from the employer's personal negligence or wilful act or default, with damages and compensation offset against each other. In a share purchase the employing company arrives with its history. Botswana counsel should confirm its effect in any deal.

• Compensation and claims: statutory compensation, common-law damages, medical costs and defence costs, for current and former workers.
• Remediation capital: South Africa halved its mining limit for respirable crystalline silica to 0.05 mg/m³ (8-hour time-weighted average) from 26 June 2025 and set a first mining limit for diesel particulate matter. Lenders applying IFC guidance may look to the ACGIH TLV of 0.025 mg/m³, half the new South African limit. Controls built for older limits may need capital the model omits.
• Productivity and skills: workers medically removed, experienced crews lost early, and scarce underground skills to replace.
• Insurability: warranty and indemnity (W&I) policies commonly exclude matters known or disclosed, and many exclude asbestos or pollution, so a liability found in due diligence usually has to be priced or indemnified.
• Finance: where a financing falls within the Equator Principles, for example project finance for a new mine or an expansion of an existing one, projects in Botswana and South Africa must meet the IFC Performance Standards. Acquisition finance falls within scope only in limited cases, such as a project originally financed under the Principles. Performance Standard 2 requires steps to prevent occupational disease and to document and report it, IFC guidance expects exposure and health monitoring data to be retained and reviewed, and many development finance lenders apply the same standards directly.
• Reputation and exit value: a disease cluster that surfaces on your watch is your story, and it will sit in the next buyer's data room.

Accounting adds a twist. Under IFRS 3 an acquirer recognises an assumed contingent liability at fair value when it is a present obligation that can be measured reliably, even if an outflow is not probable. Measuring it reliably requires exposure data.

03What conventional due diligence misses

Mining transactions run technical, financial, legal and environmental workstreams. Occupational health is often reduced to a checklist line inside the environmental and social review: is there a policy, a surveillance provider, an acceptable injury rate. Every answer can be yes while the liability remains unsized.

The technical adviser models ventilation for production, not exposure. The legal adviser reviews claims filed, not disease undiagnosed. The environmental adviser looks at the boundary, not the breathing zone. The financial adviser looks for provisions, and IAS 37 requires one only when there is a present obligation from a past event, an outflow is probable and a reliable estimate can be made. The unasked question: how many current and former workers were exposed to what, at what level, for how long, and what disease burden does that imply?

The injury rate tells you how safely the mine worked last year. It cannot tell you what the workforce breathed for the last twenty.

04An illustration: sizing a latent liability

05What exposure scientists and industrial hygienists do differently

Exposure scientists and industrial hygienists start from the premise that sparse legacy data can still support a defensible estimate, if the methods are right and the uncertainty is stated.

• Retrospective exposure assessment from surviving measurements and production, ventilation and equipment history, as the US Diesel Exhaust in Miners Study did for more than 12,000 miners.
• Similar exposure groups, each judged for compliance on its 95th percentile against the limit and characterised by its arithmetic mean for cumulative exposure, with job exposure matrices assigning exposure by job and period where individual records do not exist.
• Bayesian analysis that combines professional judgement and history with a few new measurements, including results below detection limits.
• Targeted verification sampling during due diligence, to test the legacy picture rather than accept it.
• Linkage to medical surveillance, through Occupational Medicine practitioners under medical confidentiality and reported only as anonymised results by exposure group, to see whether disease is already emerging.
• Exposure-response modelling to estimate expected cases, with Monte Carlo simulation to express the result as a range.
• Translation into deal terms and a post-completion plan for controls, surveillance and records.

06How SRG | IHH does it

Industrial Hygiene HUB delivers this as an ERITA™ (Exposure Risk Intelligence & Transaction Advisory) engagement using ERI360™, our proprietary exposure risk intelligence platform for transactions. The result is structured and repeatable, not a narrative report.

Assessments apply the ERIF™ (Exposure Risk Intelligence Framework): 32 indicators across six dimensions. Exposure covers chemical agents, physical agents, biological agents, radiation, ergonomic stressors and psychosocial stressors. Health covers acute health effects, chronic health effects, occupational disease burden, disability potential and mortality potential. Compliance covers legislative compliance, permits and licences, occupational exposure limits, monitoring programmes, medical surveillance, and training and competency. Financial covers claims and litigation, remediation cost exposure, compensation liabilities, productivity losses and insurance implications. ESG covers worker wellbeing, human capital risk, community impact, social licence to operate and ESG governance. Investment covers acquisition, reputational, financing, expansion and strategic risk.

Each indicator is scored from 0 (negligible liability) to 100 (critical liability). Unscored indicators are excluded and the weights renormalise. The engine computes the ELI™ (Exposure Liability Index), banded from Minimal to Critical Exposure Liability, and projects the index today and at year 1, year 3 and year 5 if latent liabilities are left unremediated. Deal-level readings run from negligible risk that supports the transaction without condition, through moderate risk manageable with defined remediation and high risk with material impact on valuation and deal structure, to critical liability that is likely deal-breaking without indemnity.

ERID™ (Exposure Risk Intelligence Database) builds sector benchmarks from anonymised engagement data. Its current cohorts are illustrative reference baselines, not statistical benchmarks.

The platform structures professional judgement. It does not replace it. Our team includes SAIOH registered occupational hygienists and exposure scientists, with memberships of BOHS, AIHA, ISES, ISSP and AIOH, and certified ISO 9001, 14001 and 45001 lead auditors. Samples are analysed at independent accredited laboratories. Derived financial figures are indicative decision-support outputs, not a valuation or financial advice.

07What to request in the data room

Where an item cannot be produced, the gap is itself a finding.

• The legal register of occupational health duties, and inspectorate notices from the last ten years.
• The health hazard inventory and similar exposure groups, with review dates.
• Ten years of Occupational Hygiene survey reports, with the underlying personal sampling results.
• The evidence chain behind each survey, including laboratory accreditation scope, statistical interpretation with non-detects, and noise, heat, vibration and radiation dose records, tested against the eight links in our companion article.
• The medical surveillance protocol and anonymised results by exposure group, with audiometry, lung function and radiology trends.
• Registers of occupational disease cases and compensation claims lodged, paid and pending, and any civil claims.
• Contractor exposure records and the contractual allocation of occupational health responsibility.
• Headcount history by job and period, including former employees, and where their records are kept.
• Ventilation and dust control designs, test records and capital plans against current limits.
• Workers' compensation insurance or security arrangements and claims history.

08When to engage, and why later costs more

Engage before exclusivity, when findings can still shape price and structure, and at the latest before signing. After signing, leverage is limited to protections already negotiated. After completion, a liability found is a liability owned. A remediation plan agreed at signing can be funded through the price. Discovered in year three, it competes with production for capital while claims keep accruing.

This article is general information, not legal, financial or investment advice. The illustration is hypothetical, every figure in it is an assumption, and it is not a forecast. ERI360™ outputs, including the ELI™ and derived financial figures, are indicative decision support, not a valuation. Confirm legal matters with qualified advisers in the relevant jurisdiction.

References

1. Tshiamiso Trust. Progress report, including the breakdown by country, accessed 25 September 2026. tshiamisotrust.com
2. Constitutional Court of South Africa, [2011] ZACC 3, judgment of 3 March 2011, on common-law claims by mineworkers who qualify for compensation under the Occupational Diseases in Mines and Works Act.
3. Republic of Botswana. Workers' Compensation Act (Cap 47:03), Act No. 23 of 1998.
4. Risk of silicosis in a cohort of white South African gold miners. American Journal of Industrial Medicine, 1993, 24(4): 447 to 457. pubmed.ncbi.nlm.nih.gov
5. Health and Safety Executive, 2025. Occupational Lung Disease statistics in Great Britain, 2025. hse.gov.uk
6. Republic of South Africa. Mine Health and Safety Regulations, occupational exposure limits table, Government Notice 6053, Government Gazette No. 52388, 28 March 2025.
7. International Finance Corporation, 2012. Performance Standards on Environmental and Social Sustainability. ifc.org
8. Equator Principles Association, 2020. The Equator Principles EP4. equator-principles.com
9. IFRS Foundation. IFRS 3 Business Combinations, paragraph 23. ifrs.org
10. IFRS Foundation. IAS 37 Provisions, Contingent Liabilities and Contingent Assets. ifrs.org
11. United States Government Accountability Office, February 2020. Black Lung Benefits Program: Improved Oversight of Coal Mine Operator Insurance Is Needed, GAO-20-21. gao.gov
12. National Institute for Occupational Safety and Health, 2015. Silicosis update. cdc.gov
13. Agency for Toxic Substances and Disease Registry. Case Studies in Environmental Medicine: Asbestos Toxicity.
14. American College of Occupational and Environmental Medicine. ACOEM Guidance Statement: Occupational Noise-Induced Hearing Loss. Journal of Occupational and Environmental Medicine, 2018, 60(9): e498 to e501.
15. US Bureau of Labor Statistics. Handbook of Methods, Survey of Occupational Injuries and Illnesses. bls.gov
16. The Diesel Exhaust in Miners Study: I. Overview of the exposure assessment process. Annals of Occupational Hygiene, 2010, 54(7): 728 to 746. pubmed.ncbi.nlm.nih.gov
17. Health and Safety Executive. Work-related fatal injuries in Great Britain, 2025/26. hse.gov.uk
18. International Finance Corporation, 2007. Environmental, Health, and Safety General Guidelines.
19. ACGIH. Threshold Limit Values for Chemical Substances and Physical Agents, respirable crystalline silica.