How do we decide when a chemical becomes dangerous?When does exposure become risk?And how does public health move from suspicion to regulation?

In this episode of Medlock Holmes: Global Public Health, Holmes steps into the laboratory of uncertainty - where molecules meet measurement and harm is quantified.

We explore:

• The fundamental toxicological principle: “The dose makes the poison”• Hazard identification vs risk assessment• Exposure pathways - inhalation, ingestion, dermal absorption• Acute vs chronic toxicity• Dose–response relationships and threshold models• NOAEL, LOAEL, and safety margins• Vulnerable populations and differential susceptibility• Risk characterisation and regulatory decision-making

Toxicology sits at the intersection of biology, chemistry, epidemiology, and policy. It translates laboratory data into public health protection. Yet it is rarely simple. Real-world exposures are mixed, chronic, uncertain, and socially patterned.

Holmes examines how scientists move from experimental models to population safeguards - and how precaution, evidence, and politics often intersect.

In public health, certainty is rare. Judgement must still be made.

This episode unpacks the intellectual scaffolding behind environmental standards, workplace exposure limits, food safety thresholds, and chemical regulation.

The science of harm is not just about poison - it is about proportion.

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Key Learning Threads

• Core toxicological principles• Dose–response modelling• Risk vs hazard distinction• Quantitative risk assessment framework• Safety factors and uncertainty• Translation of science into regulation• Ethical tension between precaution and proof

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