Lucas Faria da Silva

Glycemic index (GI) and glycemic load (GL) are costly to measure, yet packaged foods carry a mandatory nutrition declaration. We developed a five-parameter dilution equation that estimates GI from five label fields (available carbohydrate, total sugars, protein, fat and dietary fibre) and derives GL from it, and asked how much of the variation in GI those fields can carry. The equation was fitted to 308 foods from international GI tables, evaluated by food-family-grouped cross-validation, applied unchanged to Brazilian and South Korean cohorts (138 foods) and refitted on 305 foods with all fields measured or declared. Comparators included a published additive equation, a carbohydrate-only GL baseline and 11 machine-learning families. In development cross-validation, root mean squared error was 15.20, mean absolute error (MAE) 11.75, R2 0.213 and calibration slope 0.95; external R2 ranged from -0.08 to 0.12. Neither the learners nor eight pre-specified alternative specifications improved on the equation. GI records sharing one composition entry differed beyond measurement error in 23% of pairs, and the largest R2 attainable by any function of the five fields was estimated at 0.23 (95% CI 0.00–0.48), against 0.85 if measurement error were the only limit. Processing descriptors read from food descriptions reduced external MAE by 0.96 (95% CI 0.10–1.86). For GL, the equation was better calibrated than the additive model (slopes 1.02–1.08 versus 1.56–1.63) but not significantly more accurate than the carbohydrate-only baseline. Labels support calibrated estimates of GI and GL magnitude; further gains require information on processing and food structure.

This study quantified the activity concentrations of ²²⁶ Ra, ²²⁸ Ra, ⁴⁰ K, and the anthropogenic ¹³⁷ Cs in coffee and fresh produce from Southeastern Brazil and assessed the associated ingestion dose to consumers. Seventeen coffee samples were collected in four municipalities representing distinct geological settings, Itatiaia and Rio de Janeiro (Rio de Janeiro state) and Poços de Caldas and Mariana (Minas Gerais state), while 27 fresh-produce items were collected in the three producing municipalities (Itatiaia, Poços de Caldas, and Mariana). Activity concentrations were determined by high-purity germanium (HPGe) gamma-ray spectrometry. Annual effective doses ( E ) and the excess lifetime cancer risk (ELCR) were calculated using consumption data from the Brazilian Household Budget Survey (IBGE) and dose coefficients from ICRP Publication 119. Coffee showed mean activity concentrations of 563 ± 26 Bq kg ⁻¹ ( ⁴⁰ K), 3.7 ± 0.6 Bq kg ⁻¹ ( ²²⁸ Ra), and 1.4 ± 0.2 Bq kg ⁻¹ ( ²²⁶ Ra), with a mean annual effective dose of 3.2 × 10 ⁻⁰² mSv yr ⁻¹ . Fresh produce exhibited marked regional variability, most notably for ²²⁸ Ra: carrots from Itatiaia reached 27 ± 1.9 Bq kg ⁻¹ , nearly an order of magnitude above those from Poços de Caldas (3.3 ± 0.5 Bq kg ⁻¹ ). ¹³⁷ Cs was below the detection limit in all samples, indicating negligible anthropogenic contamination. All individual annual effective doses represented a negligible fraction of the 1 mSv yr ⁻¹ public dose criterion recommended by the ICRP. The highest individual values were observed for cassava from Mariana (1 × 10 ⁻⁰² mSv yr ⁻¹ ), followed by banana and papaya (Mariana) and orange (Itatiaia) at 9 × 10 ⁻⁰³ mSv yr ⁻¹ each, and onion from Poços de Caldas (6 × 10 ⁻⁰³ mSv yr ⁻¹ ). Cumulative annual effective doses obtained by summing all analysed fresh-produce items were 5.9 × 10 ⁻⁰² mSv yr ⁻¹ (Itatiaia), 2.2 × 10 ⁻⁰² mSv yr ⁻¹ (Poços de Caldas), and 6.3 × 10 ⁻⁰² mSv yr ⁻¹ (Mariana); combined with the mean coffee dose (3.2 × 10 ⁻⁰² mSv yr ⁻¹ ), the total remained below 1.0 × 10 ⁻⁰¹ mSv yr ⁻¹ (−07 –4 × 10 ⁻⁰⁵ for individual fresh-produce items and from 7 × 10 ⁻⁰⁵ –2 × 10 ⁻⁰⁴ for coffee. For reference, the global average ingestion dose from natural radionuclides is approximately 0.29 mSv yr ⁻¹ (UNSCEAR 2000).

This study assessed natural radioactivity and radiological risk in 48 cladding and finishing materials marketed in Rio de Janeiro State, Brazil. Activity concentrations of 226Ra, 232Th and 40K were measured by high-resolution gamma-ray spectrometry using a 30% relative-efficiency HPGe detector, and radiological indices and annual effective dose were calculated. Mean activities were 23.2 ± 25.0, 31.2 ± 52.8 and 163.3 ± 309.0 Bq kg-1 for 226Ra, 232Th and 40K, respectively. Mean radium equivalent activity was 80.4 ± 112.3 Bq kg-1 and mean annual effective dose was 0.34 ± 0.46 mSv y-1. Non-parametric comparisons showed a clear activity gradient among functional groups (G1 > G2 > G3; p < 0.001), with mean doses of 0.679, 0.118 and 0.039 mSv y-1, respectively. Principal component analysis showed that one component explained 89.1% of the variance, while hierarchical clustering reproduced the functional classification for 42 of 48 samples (adjusted Rand index = 0.688), supporting a common underlying radioactivity gradient. Fifteen samples exceeded the conservative dose screening level of 0.48 mSv y-1, all in G1, and two mortars exceeded 1 mSv y-1. However, under the Radiation Protection 112 activity-index criterion for superficial materials, no sample exceeded the limit associated with 1 mSv y-1. Radiological concern is therefore concentrated in a limited subset of G1 products, particularly mortars and phyllite clays, supporting targeted raw-material selection and quality control.

Building materials are a primary source of indoor exposure to naturally occurring radioactive materials (NORMs), yet existing regulatory frameworks lack practical, cost-based tools to support the implementation of the ALARA principle in the construction sector. This study introduces the Ionizing Radiation Index (Γioniz), a novel approach that converts annual effective dose into a monetary value (US$), enabling transparent radiological risk classification of building materials. Activity concentrations of 226Ra, 232Th, and 40K were measured in 266 samples of 50 building material types, organized into eight groups (G1–G8) and collected from construction sites and stores in Rio de Janeiro, Brazil, between July 2020 and August 2024. Measurements were carried out using high-purity germanium (HPGe) gamma spectrometry after secular equilibrium between 238U, 232Th, and their decay products was confirmed. A log-normal distribution provided an adequate fit for all radionuclides (Kolmogorov–Smirnov test, p > 0.05 for all variables). The overall mean annual effective dose was 0.37 ± 0.02 mSv y-1. Group G1 — comprising crushed stone, sand, cement, and brick — recorded the highest Γioniz (US$ 90.39, classified as high radiological cost), followed by G3 (US$ 62.02), while G8 (paints and coatings) presented the lowest value (US$ 5.05). Materials are classified into three tiers: low risk (Γioniz ≤ US$ 30, E ≤ 0.3 mSv y-1), moderate risk (US$ 30 < Γioniz ≤ 60, 0.3 < E ≤ 0.6 mSv y-1), and high risk (Γioniz > US$ 60, E > 0.6 mSv y-1). The Γioniz framework offers regulators and industry stakeholders a financially grounded, ALARA-aligned instrument for regulatory impact analysis and informed material selection in residential construction.

Gamma-ray spectrometry is an essential analytical technique in environmental studies, providing valuable insights into radionuclides in building materials. This method enables researchers to assess potential radiation exposure and ensure compliance with safety regulations. By identifying specific isotopes, scientists can evaluate the radiological impact on public health and the environment. It uses the energy spectrum of emitted gamma rays to determine the type and quantity of isotopes present in samples. This study applies gamma-ray spectrometry to quality testing through case studies of commonly used building material samples in Brazil, using ISO and ABNT NBR standards as parameters. The main results discussed here demonstrate the potential for the development of gamma-ray spectrometry in the civil construction field. The identification of radioisotopes, the relationship between radionuclides and the standard composition of the samples, and the simplification of processes for obtaining results were fundamental to ensuring the quality and application of the technique. Although it has limitations, such as the need for large amounts of data, skilled labor, and proper sample preparation, the technique represents a significant improvement over current analytical methods, offering advantages in non-destructiveness and multi-elemental simultaneous detection compared to X-ray Fluorescence (XRF), Energy Dispersive Spectroscopy (EDS), and X-ray Diffraction (XRD), while also providing radiological characterization not accessible through those techniques, as well as in environmental sciences. In this context, the results showed that some building materials—such as sands, mortars, granites, enamel paints, and bricks—exhibit significant compositional differences from standard materials, as detected through gamma spectra and peak counting. These anomalies may compromise structural integrity and pose risks in Brazilian dwellings.

To assess radiation risks in building materials, this study presents an analysis framework that considers dose, exposure time, and frequency of material use, and develops a risk assessment and management model based on a management table and the temporal formula for material use in dwellings. Additionally, a cost-benefit analysis was employed to validate the risk assessment and management approach. First, the risk matrix classifies materials according to dose limits; then, usage time indicates the maximum exposure period during which a person could be exposed for up to 80% of their lifetime. The mean activity concentrations of 226Ra, 232Th, and 40K in the samples ranged from 1.3 ± 0.4 to 94.3 ± 2.5, 0.74 ± 0.4 to 91.7 ± 0.9, and 1.2 to 1023 ± 44 Bq kg-1, respectively. The effective dose ranged from 0.011 ± 0.001 to 1.094 ± 0.02 mSv y-1, with a mean value of 0.342 mSv y-1, which is above the recommended exclusion value of 0.3 mSv y-1 and below the dose limit of 1.0 mSv y-1 for most materials. However, regular monitoring of radioactivity levels in geological materials from sources is recommended before their use in construction. The results indicate that sand, cement, crushed stone, bricks, and some porcelain tiles present the highest risk under the established conditions. A cost-benefit analysis indicated that glass sand can replace river sand commonly used in dwellings, reducing radiation exposure risk and providing positive environmental impact by reusing materials and lessening the effects of river sand extraction. An appropriate agency should be established to consistently monitor radiation and prevent related health problems. The constructed model can offer new insights for radiation risk assessment in environmental analysis. These results are significant for the safety of materials in the Brazilian construction sector and may provide information to support radiological risk management.

This study aims to provide a thermophysical characterization of crushed stone, sand, brick, and cement due to radioactive decay. The 28 sand samples, 23 cement samples, 30 crushed stone samples, and 29 brick samples were analyzed by X-Ray Fluorescence (XRF) and Scanning Electron Microscope (SEM) coupled with Energy-Dispersive X-ray Spectroscopy (EDS) to screen samples for the presence of uranium, potassium, and thorium. Also high-purity germanium (HPGe) gamma spectrometers were applied to estimate 226Ra (as a proxy for the 238U decay series), 40K, and 232Th contents in ppm and to evaluate heat generation generated in the samples. For the samples, 226Ra ranges from 0.68 ± 0.04 to 21.7 ± 0.47 ppm, 40K ranges from 428 ± 92 to 37172 ± 1651 ppm, and 232Th ranges from 0.86 ± 0.11 to 171 ± 0.24 ppm. 21 sand samples, 19 cement samples, 29 crushed stone and stone dust samples, and 13 brick samples presented values ​​above the recommended average. The IH varied from 6.27×10-4 to 0.34, and the radiogenic heat production between the materials varied from 0.04 to 0.88 μW m-3, exceeding the average value ​​of 0.5 μW m-3 observed by Hansi Junior & Kusznir (2025). The temperature generated (Ttrmc) due to the radioactive decay of these materials in use in a standard room in a house was 7.54×10-5 °C. The value of the thermal power generated in the wall, the heat generation produced by the consumed mass, the linear power density, and the heat flux that passes through the wall surface from these materials were 3.65 μW, 1.98 nW kg-1, 0.46 µW m-1 and 0.23 µW m-2, respectively. The primary chemical components in the samples media are SiO2, Fe2O3, K2O and Al2O3. The crystal structures of samples typically consist of alternating Si-O tetrahedral layers and Al-O octahedral layers. The findings from this research will be useful to assess the radiation hazards of building materials in humans.