This study investigated the efficiency of a sequestration strategy using carbon-based materials to reduce the transfer of organochlorine pesticides (OCPs) from hens to eggs. Specifically, the potential of Kazakhstan-made Shoptykol coal was evaluated by applying 2% (by weight) of this material to OCP-contaminated soil obtained from Kyzylkairat (Almaty region, Kazakhstan). The experiment was conducted by exposure for 45 days of 18 hens, which were divided into three groups depending on their feeding conditions. Laying hens were fed diets containing 10% of soil: for the first group with control soil A, the second group with contaminated soil K, the third group with contaminated soil containing coal. Quantification of pesticide concentrations in egg yolks of laying hens was then performed by gas chromatography mass-spectrometry. Despite the supply of Shoptykol, no significant reduction in OCPs transfer was observed for compounds tested. Thus, the efficiency of Shoptykol coal in reducing the transfer of organochlorine pesticides to animals was not confirmed by our results.

Free-ranging poultry ingest 4–30 g of soil per day, making soil a significant route of organochlorine pesticide (OCP) exposure in agricultural areas with legacy contamination. However, total soil concentrations overestimate actual exposure. Only the bioaccessible fraction, mobilized within the gastrointestinal tract, governs transfer to eggs and meat. Static physiologically based extraction test (PBET) models consistently underestimate this fraction for hydrophobic compounds due to re-equilibration of desorbed contaminants onto the soil matrix. This study applied and evaluated a sink-modified static in vitro gastrointestinal model incorporating Tenax resin as a sorption sink to assess OCP bioaccessibility in spiked aged soil under simulated poultry digestive conditions. The aqueous phase-only fraction (gastric plus intestinal liquid) ranged from 0.004 to 17.1%, while the aqueous phase plus sorption sink (Tenax) fraction, measured from the same intestinal phase incubation, ranged from 24.0 to 52.7%, with the largest relative changes observed for HCH isomers (from near-undetectable levels without Tenax) and 2.7- to 4.3-fold increases for DDT-related compounds, a difference confirmed as statistically significant (paired t-test) for six of the seven compounds. One-way ANOVA revealed significant differences among compounds (F(6,21) = 5.53, p = 0.0014). Tukey’s HSD showed that β-HCH (56.1 ± 10.6%) and 4,4′-DDT (55.6 ± 24.0%) had significantly higher bioaccessibility than γ-HCH (25.8 ± 0.9%), 2,4′-DDD (22.2 ± 18.0%), and 4,4′-DDE (22.0 ± 5.7%), while α-HCH (28.6 ± 3.9%) and 4,4′-DDD (33.9 ± 8.1%) occupied an intermediate position, not significantly different from either group. A substantial fraction of mobilized OCPs was associated with the Tenax sink (17–53%), confirming that aqueous phase measurements alone underestimate the bioaccessible pool. These results demonstrate the importance of including a sorption sink in poultry-informed gastrointestinal models for accurate assessment of OCP transfer from contaminated soil to food products.