Understanding the Latest Research on PAHs in Singapore's Diet
The recent publication in Scientific Reports has brought attention to polycyclic aromatic hydrocarbons (PAHs), a group of persistent environmental pollutants known for their potential carcinogenic properties. This probabilistic dietary exposure assessment, drawing data from Singapore's Total Diet Study (TDS) conducted between 2021 and 2023, highlights varying levels of PAHs in everyday local foods.
Singapore's TDS represents a comprehensive effort to map chemical hazards in foods as they are typically consumed, reflecting real-world preparation and eating habits. By analyzing pooled samples from 281 foods across 22 categories, the initiative establishes a baseline for dietary exposure that informs public health strategies. This research underscores the pivotal role of higher education institutions like NUS and NTU in advancing food safety science through interdisciplinary collaboration.
What Are Polycyclic Aromatic Hydrocarbons (PAHs)?
Polycyclic aromatic hydrocarbons (PAHs) are a class of organic compounds consisting of two or more fused aromatic rings, formed primarily through incomplete combustion of organic materials. Common sources include vehicle exhaust, industrial processes, tobacco smoke, and high-temperature food cooking methods like grilling, smoking, or frying. In the food chain, PAHs can contaminate through environmental deposition, processing, or direct formation during cooking.
The study focused on four indicator PAHs—benz[a]anthracene (BaA), benzo[a]pyrene (BaP), benzo[b]fluoranthene (BbF), and chrysene (CHR)—due to their established genotoxicity and carcinogenicity by international bodies like the International Agency for Research on Cancer (IARC). BaP, for instance, is classified as Group 1 carcinogenic to humans. These compounds are lipophilic, accumulating in fatty foods and posing chronic risks via dietary intake, which accounts for a significant portion of non-occupational exposure in urban settings like Singapore.
In Singapore's context, where seafood, stir-fried dishes, and imported processed foods dominate, understanding PAH pathways is vital. The SFA actively monitors such contaminants, integrating findings into regulatory frameworks to protect consumers.
Background on Singapore's Total Diet Study (TDS)
Initiated in 2021 by the SFA in partnership with NUS and Temasek Polytechnic, the TDS involved a nationwide food consumption survey of 2,014 residents aged 15 and above. Using 24-hour recall methods, researchers identified top-consumed foods contributing over 90% of dietary weight across demographics, including Chinese, Malay, Indian, and others.
Samples were procured from wet markets, supermarkets, and online platforms, then prepared using standardized household methods—washing, peeling, cutting, and cooking (e.g., stir-frying, steaming). Pooled analyses at SFA's ISO-accredited labs targeted over 100 chemicals, including heavy metals, PFAS, mycotoxins, and PAHs. This 'as-consumed' approach distinguishes TDS from traditional monitoring, providing realistic exposure estimates.
The TDS complements SFA's Market Monitoring Programme (MMP), enabling integrated risk assessment from retail surveillance to human biomonitoring.
Methodology of the PAHs Probabilistic Exposure Assessment
The core study employed Monte Carlo simulation for probabilistic modeling, incorporating variability in PAH concentrations, food consumption, and body weights. Data inputs stemmed from TDS: mean PAH levels in 22 food categories, paired with consumption patterns from the survey.
Two scenarios were modeled—optimistic (lower-bound concentrations) and pessimistic (upper-bound)—to capture uncertainty. Exposure was chronic (lifetime average daily intake, LADI), calculated as sum PAHs (ng/kg bw/day). Cancer risk used potency factors from California's Office of Environmental Health Hazard Assessment; disease burden via Disability-Adjusted Life Years (DALYs), Singapore population (5.92 million).
- Food sampling: 15 sub-samples per item, pooled post-preparation.
- Analysis: Validated methods with low LODs/LOQs for PAHs.
- Simulation: 10,000 iterations for robust distributions.
Affiliations highlight academic contributions: NUS's Food Science & Technology Department provided analytical expertise, while NTU's School of Biological Sciences supported lead author Kyaw Thu Aung.Explore research positions in food science at Singapore universities.
Photo by adison clark on Unsplash
Foods with Elevated PAH Levels Identified
TDS results pinpointed higher PAH concentrations in specific categories: nuts and seeds (e.g., roasted peanuts), sauces and condiments (soy, oyster), fruiting vegetables (e.g., chilies, eggplants), fungi, and seaweed. Fats/oils and ready-to-eat savouries also showed notable levels, up to 2.9 ppb mean sum PAHs.
Seafood stood out due to cooking effects: stir-fried fish had higher PAHs than boiled or steamed, linking preparation habits to exposure. These findings reflect Singapore's cuisine—heavy on stir-fries and condiments—necessitating targeted interventions.
Compared to raw states, cooking amplified PAHs in some items, emphasizing household practices in risk profiles.
Dietary Exposure Estimates for Singaporeans
Probabilistic modeling yielded LADI ranges reflecting consumption variability. Optimistic scenario: lower exposures dominated by moderate consumers; pessimistic captured high-intake tails (e.g., heavy seafood eaters).
Key contributors: sauces/condiments (20-30%), nuts/seeds (15-25%), seafood (10-20%). Children and adults showed similar patterns, adjusted for body weight. Overall, exposures align with or below regional peers, crediting SFA import controls.
Assessing Health Risks: Cancer and Disease Burden
Lifetime cancer risk (ILCR) spanned 4.63 × 10-5 (optimistic) to 5.17 × 10-3 (pessimistic), with BaP as primary driver. Acceptable risk thresholds (10-6 to 10-4) indicate low-moderate concern for most, though upper bounds warrant vigilance.
Population DALYs: 0.236 to 92.5 years, translating to negligible per capita impact (4 × 10-8 to 1.56 × 10-5 DALYs/person/year). This low burden reflects effective controls, yet vulnerable groups (e.g., frequent grillers) merit focus.
SFA notes typical diets pose minimal risk, echoing global views where dietary PAHs contribute modestly to total exposure.
Cooking Methods and PAH Formation: Practical Insights
SFA guidance emphasizes mitigation: PAHs form via pyrolysis in high-heat, fat-dripping scenarios. Tips include:
- Prefer steaming/boiling over stir-frying/grilling for seafood/meat.
- Trim fat, flip frequently, use electric grills.
- Avoid charred bits; ventilate to reduce smoke inhalation.SFA cooking safety page
TDS validated these, showing stir-frying elevates PAHs in fish by 2-3x.
Photo by Natália Catunda on Unsplash
Role of NUS and NTU in Food Safety Research
NUS researchers, including from Food Science & Technology and Public Health, contributed analytical methods and epidemiological modeling. NTU's involvement via Kyaw Thu Aung bridges biology and toxicology. This collaboration exemplifies Singapore's RIE2030 investments in applied research.
Such studies position Singapore universities as leaders. Aspiring academics can find opportunities in Singapore higher ed jobs and research roles.
Implications and Future Directions
The study advocates continued monitoring, refined standards, and consumer education. SFA's integrated approach—MMP, TDS, biomonitoring—ensures agility against emerging risks like climate-impacted contaminants.
Future: longitudinal TDS, expanded PAHs (16 EPA priorities), vulnerable subgroup analyses. For researchers, this opens avenues in toxicology and public health.Postdoc opportunities in Singapore.
Consumers: diversify diets, adopt low-PAH cooking. AcademicJobs.com supports careers advancing such science—check Rate My Professor, higher ed jobs, career advice.
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