Hair Toxicology: Core Lecture Notes (copy)

long-term biological archive

Hair that serves as a record of drug exposure through trapped parent drugs and metabolites.

keratinized shaft

The part of hair that captures and locks in chemicals during growth.

parent drugs

The original drugs that are metabolized and can be detected in hair.

metabolites

The substances formed from the metabolism of drugs that can also be captured in hair.

retrospective calendar of exposure

The ability of hair to provide a history of substance exposure over time.

ethyl glucuronide

A metabolite of alcohol that can be found in hair.

fatty-acid ethyl esters

Compounds that indicate alcohol use and can be collected from hair.

GHB

Gamma-Hydroxybutyric acid, relevant in investigations of drug-facilitated sexual assault (DFSA).

drug-facilitated sexual assault (DFSA)

Criminal acts where substances are used to intoxicate victims.

distance from the scalp

Used to estimate the time that has passed since drug ingestion based on hair growth.

hair growth rate

The speed at which human hair grows, averaging from 6 mm to 33.6 mm per month.

classroom rule of thumb for growth rate

Average hair growth is approximately 10 mm (1 cm) per month.

Time Calculation Formula

Time (months) = Distance from root (mm) / Growth rate (mm month^{-1}).

DFSA hair collection timing

Collect hair 1–3 months after assault to maximize the likelihood of detecting drugs.

segmentation

Cutting hair into 1–2 cm sections for chronological analysis.

decontamination (washing)

Process of cleaning hair samples to remove external residues.

endogenous incorporation

The measurement of naturally integrated substances rather than external contamination.

analysis considerations

Factors such as drug absorbance efficiency and contamination that must be accounted for in testing.

individual variability in growth rate

Differences in hair growth speed among individuals that can impact drug analysis.

external contamination

Substances that are not ingested but found in hair, complicating drug evidence.

ethical implications

The moral concerns surrounding privacy issues in long-term substance monitoring.

informed consent

The process of obtaining permission from individuals before conducting monitoring.

critical formula for estimating drug use time

Time (mo) = Segment centroid distance (mm) / Growth rate.

3 cm hair sample window

Captures an approximate 3-month window of substance use.

matrix effects

Variations in drug detection efficiency due to the composition of hair samples.

thorough washing

A necessary step to clarify true drug ingestion versus contamination.

window of drug detection

The period during which drug use can be accurately traced through hair analysis.

chemical anchoring

The process of drugs and their metabolites becoming embedded in hair strands.

drug exposure timeline

A chronological representation of drug use based on the growth segments of hair.