How does birch tar affect mice? - briefly
Birch tar exhibits acute toxicity in mice, leading to neurological disruption, reduced locomotor activity, and dose‑dependent mortality. It also functions as an effective repellent, decreasing rodent attraction to treated areas.
How does birch tar affect mice? - in detail
Birch tar, a complex mixture of phenolic compounds, polycyclic aromatic hydrocarbons, and fatty acids, exerts multiple physiological and toxicological effects on laboratory mice when administered orally, dermally, or via inhalation.
Acute exposure studies reveal dose‑dependent central nervous system depression, manifested by reduced locomotor activity, diminished reflexes, and, at high concentrations, loss of righting reflex. Respiratory irritation appears rapidly, with increased respiratory rate and nasal discharge. Mortality rates correlate with administered dose, with LD₅₀ values reported between 1.2 g kg⁻¹ and 1.8 g kg⁻¹ for oral ingestion.
Sub‑chronic investigations (28‑day exposure) document the following alterations:
- Hepatic enzyme induction: elevated cytochrome P450 activity, increased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) serum levels.
- Hematological changes: mild anemia, reduced erythrocyte count, and altered leukocyte differential suggesting immunomodulation.
- Dermatological effects: erythema, hyperkeratosis, and delayed wound healing on sites of topical application.
- Behavioral modifications: increased anxiety‑like behavior in elevated plus‑maze tests, reduced exploratory activity in open‑field assays.
Chronic exposure (90 days or longer) is associated with:
- Carcinogenic potential: formation of preneoplastic lesions in the forestomach and increased incidence of hepatic adenomas in high‑dose groups.
- Reproductive toxicity: decreased sperm count, impaired motility, and reduced litter size in breeding pairs exposed to sub‑lethal concentrations.
- Neurodegeneration: accumulation of lipofuscin granules in hippocampal neurons, accompanied by deficits in spatial memory tasks.
Metabolic profiling indicates that phenolic constituents undergo hepatic conjugation, producing glucuronide and sulfate metabolites excreted in urine. Polycyclic aromatic hydrocarbons persist longer, forming DNA adducts that contribute to mutagenic outcomes.
Risk assessment models extrapolate murine data to estimate human occupational exposure limits, emphasizing the necessity of ventilation controls and personal protective equipment when handling birch tar in industrial settings.