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Pasteurized Milk Quality Evaluation and Health Risk Assessment of Heavy Metals Using Monte Carlo Simulation and Sensitivity Analysis in Iran Market

This study evaluates heavy metal contamination in Iranian pasteurized milk and, using Monte Carlo simulation, finds that while non-carcinogenic risks are low, moderate carcinogenic risks exist for both children and adults, primarily driven by arsenic exposure, necessitating continuous monitoring to ensure food safety.

Original authors: Zahra Alinezhad, Mohammad Hashemi, Mostafa boskabadi, Saeid Khanzadi, Seyedeh belin Tavakoly sany

Published 2026-07-07

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CC BY 4.0

Original authors: Zahra Alinezhad, Mohammad Hashemi, Mostafa boskabadi, Saeid Khanzadi, Seyedeh belin Tavakoly sany

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine milk as a daily delivery truck bringing essential nutrients to our bodies. This study acts like a quality control inspector, checking that truck for hidden, dangerous cargo: heavy metals like lead, mercury, and arsenic. The researchers wanted to know: Is the milk we buy in Iranian supermarkets safe, or is it secretly carrying a toxic load that could hurt us over time?

Here is a breakdown of their investigation, using simple analogies:

1. The Investigation (The "Sniff Test")

The team collected 216 cartons of pasteurized milk from nine different popular brands. They didn't just check once; they checked four times over the course of a year (Winter, Spring, Summer, Autumn) to see if the weather or the season changed the "cargo."

They tested for 11 different metals. Think of these metals as different types of unwanted passengers on the milk truck. Some are common (like Zinc and Iron), while others are notorious troublemakers (like Lead, Mercury, and Arsenic).

2. What They Found (The "Passenger Manifest")

The Good News: One dangerous passenger, Cadmium, was completely missing from every single carton. It was as if the truck was empty of this specific threat.
The Bad News: Three troublemakers showed up more often than allowed:
- Lead (Pb): Found in higher amounts than safety standards allow.
- Mercury (Hg): Found in higher amounts than allowed, but mostly in the winter.
- Copper (Cu): Found in excess during the cold seasons (Winter and Autumn).
The Seasonal Twist: The "passengers" changed depending on the time of year.
- Winter/Autumn: The cold weather seemed to bring in more Copper, Iron, and Chromium. The researchers suggest this might be like rain washing industrial waste into the water sources that cows drink.
- Spring/Summer: The warmer months brought in more Arsenic and Lead. This might be because cows eat more fresh grass and drink more water during these seasons, picking up pollutants from the soil and air.

3. The Health Check (The "Risk Calculator")

The researchers didn't just count the metals; they calculated the risk to human health using a sophisticated computer simulation called Monte Carlo. Imagine this as running a simulation 10,000 times to see how likely it is that drinking this milk causes harm.

They looked at two types of risks:

Immediate Danger (Non-Carcinogenic Risk): This asks, "Will drinking this milk make you sick right now?"
- Result: Safe. The risk score was below 1 for both children and adults. It's like saying the truck isn't carrying a bomb that will explode today.
Long-Term Danger (Carcinogenic Risk): This asks, "If you drink this milk every day for years, what are the odds of getting cancer?"
- Result: Moderate Concern. The risk wasn't zero. The study found a "moderate" level of cancer risk.
- The Analogy: If you imagine a lottery where winning means getting cancer, the study suggests that for every 10,000 children drinking this milk, about 1 might develop cancer due to these metals. For 100,000 adults, about 7 might be at risk. While this sounds small, in public health, it's considered a "moderate" risk that shouldn't be ignored.

4. The Main Culprit (The "Mastermind")

When the researchers ran a "sensitivity analysis" (a way to see which variable matters most), they found that Arsenic was the biggest driver of the cancer risk.

Even though Lead and Mercury were also present, Arsenic was the "mastermind" behind the danger. It was the most influential factor in making the risk score go up.
Think of it like a team of thieves: Lead and Mercury are the lookouts, but Arsenic is the one actually breaking the bank.

5. The Conclusion (The "Verdict")

The paper concludes that while the milk isn't immediately toxic (you won't get sick today), it is not perfectly safe for long-term consumption due to the potential for cancer.

The Problem: The milk contains heavy metals (Lead, Mercury, Copper, and Arsenic) at levels higher than international safety guidelines.
The Cause: This likely comes from a mix of environmental pollution (air, water, soil) and the equipment used to process and package the milk.
The Recommendation: The authors suggest that we need continuous monitoring. Just because the truck passed inspection today doesn't mean it will tomorrow. We need to keep checking the milk to ensure the "cargo" remains safe for our families.

In short: The milk is nutritious, but it's carrying a hidden, slow-acting poison that increases cancer risk slightly over a lifetime. The study urges authorities to keep a close watch on the milk supply to keep that risk as low as possible.

Technical Summary: Pasteurized Milk Quality Evaluation and Health Risk Assessment of Heavy Metals Using Monte Carlo Simulation and Sensitivity Analysis in Iran Market

Problem Statement
Food safety is a critical determinant of public health, particularly regarding the control of chemical pollutants in essential dietary components like milk. While milk is a primary source of nutrients, it acts as a potential carrier for toxic heavy metals and metalloids (such as arsenic) originating from environmental pollution, industrial activities, and processing equipment. Despite the significance of milk consumption in Iran (approximately 25.05 kg per capita annually), there is a notable gap in comprehensive research assessing the levels of heavy metals and their associated health risks in commercial pasteurized milk brands available on the Iranian market. Existing literature has largely focused on raw milk or limited metal types, leaving the specific risks of carcinogenic and non-carcinogenic exposure from commercial pasteurized products insufficiently characterized.

Methodology
The study employed a rigorous quantitative approach to evaluate heavy metal contamination and associated health risks:

Sampling: A total of 216 pasteurized milk samples were collected from nine prominent commercial brands across Iran. The sampling design covered four seasons (winter, spring, summer, autumn) from winter 2021 to autumn 2022. The samples included two fat variations: low-fat (1%) and full-fat (3%), with 108 samples of each type.
Analytical Techniques: Heavy metals (Fe, Al, Ni, Cu, Pb, Zn, Hg, Cd, Co, Cr, and As) were quantified using Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) following acid digestion. Method validation included the use of Certified Reference Materials (CRMs) and recovery rate checks (80–120%).
Risk Assessment Models:
- Non-Carcinogenic Risk: Calculated using the Estimated Daily Intake (EDI), Hazard Quotient (THQ), and Hazard Index (HI) based on US EPA guidelines.
- Carcinogenic Risk: Evaluated for Arsenic (As), Lead (Pb), and Mercury (Hg) using cancer slope factors (OSF).
- Probabilistic Modeling: To address uncertainties inherent in point estimates, the study utilized Monte Carlo simulation (10,000 iterations via Crystal Ball software) to model risk distributions.
- Sensitivity Analysis: Conducted to determine the relative influence of input variables (metal concentration, consumption rate, body weight, exposure duration) on the final risk outcomes.

Key Results

Contamination Levels:
- Cadmium (Cd): Detected below the limit of detection in all samples.
- Exceedance of Standards: The average concentrations of Lead (Pb), Mercury (Hg), and Copper (Cu) exceeded the standards set by the World Health Organization (WHO) and Food and Agriculture Organization (FAO) across all seasons. Specifically, Cu levels exceeded the 0.2 mg/L limit in autumn and winter; Pb exceeded the 0.02 mg/L limit in 19 samples; and Hg exceeded the 0.01 mg/L limit in 100% of detected samples.
- Seasonal Variations: Significant differences ( $p < 0.05$ ) were observed for Al, As, Cr, Cu, Fe, and Zn. Higher concentrations of most metals (Al, Cr, Cu, Fe, Zn) were recorded in cold seasons (winter/autumn), while Arsenic levels peaked in spring.
- Fat Content: No significant difference ( $p > 0.05$ ) in heavy metal concentrations was found between low-fat and full-fat milk types.
Health Risk Assessment:
- Non-Carcinogenic Risk: The Hazard Index (HI) for both children and adults was below the threshold of 1 ($HI < 1$) across all seasons, indicating no significant non-carcinogenic risk from the consumption of these pasteurized milk samples.
- Carcinogenic Risk: The Total Carcinogenic Risk (TCR) fell within the "moderate" range ( $10^{-4}$ to $10^{-6}$ ). The average probability risk was $1.41 \times 10^{-4}$ for children and $6.7 \times 10^{-5}$ for adults. This suggests a potential risk where approximately 1 in 10,000 children and 7 in 100,000 adults could develop cancer due to heavy metal exposure from milk.
Sensitivity Analysis: Arsenic (As) was identified as the most influential variable in developing carcinogenic risk, contributing approximately 89% to the risk in both age groups. Other parameters had an impact of less than 15%.

Significance and Claims
The paper asserts that while pasteurized milk in the Iranian market does not pose an immediate non-carcinogenic threat, there is a potential moderate risk of cancer associated with the consumption of these products due to heavy metal contamination. The study highlights that the presence of metals such as Lead, Mercury, and Copper, alongside the highly influential Arsenic, renders the samples unsafe regarding potential cancer risks.

The authors conclude that the current findings underscore the necessity for continuous monitoring of milk and dairy products for heavy metal content. They emphasize that such monitoring is essential not only for maintaining food safety but also for providing data-driven evidence to support decision-making aimed at promoting human health. The study positions itself as a critical step toward understanding the specific health implications of commercial milk consumption in Iran, bridging a gap in regional literature regarding carcinogenic risk assessments using probabilistic modeling.

1. The Investigation (The "Sniff Test")

2. What They Found (The "Passenger Manifest")

3. The Health Check (The "Risk Calculator")

4. The Main Culprit (The "Mastermind")

5. The Conclusion (The "Verdict")

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