Evaluating lead leaching from uPVC pipes into drinking water: Characterization with SEM-EDX and ICP-OES

The goal of this study is to investigate the presence and leaching rate of lead from locally sourced unplasticized polyvinyl chloride (uPVC) pipes into drinking water under different temperature and time conditions. The study addresses a gap in existing literature by focusing on uPVC pipes manufactured with region-specific processes and materials, providing insights relevant to local public health and regulations.

A dual-method approach is used: inductively coupled plasma optical emission spectrometry (ICP-OES) quantifies lead concentrations in water, while scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) maps the distribution of lead on pipe surfaces. This combined methodology offers a comprehensive understanding of lead leaching dynamics and supports the evaluation of potential health risks associated with local uPVC piping systems.

The original article

Evaluating lead leaching from uPVC pipes into drinking water: Characterization with SEM-EDX and ICP-OES

Yassin T.H. Mehdar

Results in Chemistry, Volume 13, 2025, 101976

https://doi.org/10.1016/j.rechem.2024.101976

licensed under CC-BY 4.0

Selected sections from the article follow. Formats and hyperlinks were adapted from the original.

Unplasticized Polyvinyl Chloride (uPVC) is a versatile and widely used material in the construction and plumbing industries due to its durability, resistance to weather, and low maintenance requirements. At the core of uPVC's performance and reliability is the use of stabilizers, which enhance the material's stability and improve its processing characteristics. One such stabilizer is Lead (Pb), a heavy metal that has been used in uPVC manufacturing for its unique properties [1], [2], [3], [4].

The use of Lead (Pb) as a stabilizer in uPVC is a complex process that involves several steps. First, the raw materials, including PVC resin, stabilizers, and other additives, are meticulously mixed. Lead (Pb) is introduced at this stage as it plays a crucial role in enhancing the stability and processability of the uPVC. Next, the mixture is processed under high temperatures and pressures to form a homogenous compound. This step is critical as it determines the final properties of the uPVC. The high temperatures not only facilitate the melting and mixing of the components but also aid in the dispersion of Lead (Pb) throughout the compound. After the compound formation, the uPVC is extruded into the desired shape, such as pipes or profiles. At this stage, the presence of Lead (Pb) as a stabilizer becomes evident as it helps maintain the shape and dimensional stability of the uPVC during the extrusion process [5], [6], [7].

A recent study in 2023 examines the factors affecting the release of lead and iron from Egyptian water pipes made of PVC, PP, and GI. Low pH increased lead release, with PVC pipes showing lead concentrations of 0.09–0.13 mg/L, PP pipes 0.03–0.04 mg/L, and GI pipes 0.053–0.064 mg/L after 72 h of stagnation. Higher pH and alkalinity reduced metal release. PVC pipes released the most lead, and PP pipes the least. Findings emphasize the significant influence of water chemistry on metal leaching in water supply systems [23]. Moreover, a study examined the impact of water pH and flow conditions on lead release from PEX-A, HDPE, and copper pipes. Lead release was higher at pH 5.0 and under stagnant conditions. Biofilm-laden HDPE pipes released 5.3 % lead over 120 h, while biofilm-laden copper pipes released 3.9 % lead in 6 h. New PEX-A pipes released 4.4 % lead under flow conditions. Biofilms did not significantly affect lead uptake [24].

This paper will thoroughly study these aspects and investigate the presence of lead and its leaching rate from some uPVC pipes into drinking water undergoes different conditions of temperature and time. In addition, this study includes a characterization method of elemental mapping obtained using scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX). Furthermore, inductive coupled plasma-optical emission spectrometry (ICP-OES) was utilized to determine the concentration of Pb in water samples.

Materials and methods

ICP-OES characterization

Inductively coupled plasma-optical emission spectrometry (ICP-OES; Thermo Scientific, ICAP 6000 Series) was employed to quantify the concentration of Pb in water samples. The instrument operated with a radio frequency (RF) power of 1.2 kW, an argon coolant gas flow rate of 18 L/min, and a gas pressure of 30 psi. The water samples were acidified using HNO₃ (Sigma-Aldrich), and the final volume of each sample was concentrated to 22 ml. Thereafter, the samples were analyzed using ICP-OES.

SEM-EDX characterization

The SEM-EDX laboratory conditions were controlled, with a constant temperature of 27 ± 1°C and relative humidity maintained between 40–46 %. The SEM-EDX analysis was performed using an emission scanning electron microscope (SEM, Hitachi TM 3030 Plus) equipped with EDX microanalysis system was utilized to quantify the weight percentages of Lead (Pb) on the inner surfaces of the uPVC pipes. The SEM was employed in high vacuum mode with an accelerating voltage of 15 kV. Each uPVC pipe was examined at multiple magnifications (100x, and 600x) to capture surface morphology and structural details.

Results and discussions

Elemental composition of uPVC pipes

Results show the elemental mapping of the inner surfaces of the three uPVC pipes (uPVC1, uPVC2, and uPVC3) obtained using the SEM equipped with EDX microanalysis system, in which surface distributions (Fig. 1, Fig. 2). The weight percentage of the main components in these pipes was determined at two different measurement points (magnitude 100 × and 600 × ).

Results in Chemistry, Volume 13, 2025, 101976: Fig. 1. SEM-EDX elemental mapping for uPVC pipes used in this study (a) uPVC1, (b) uPVC2, and (c) uPVC3, at Magnitude 100x.

Influence of storage time on lead release

In this study, the influence of time on lead release was significant, with lead concentrations increasing over time. For example, at 40 °C, the concentration of lead in uPVC1 on day 3 was twice that on day 1, and it further increased fivefold by day 10. At 50 °C, the lead concentration in uPVC1 rose from 37 µg/L on day 1 to 206 µg/L by day 10. Similarly, for uPVC2 and uPVC3 at 40 °C, lead concentrations increased from 43 µg/L and 40 µg/L on day 1 to 214 µg/L and 224 µg/L by day 10, respectively.

These findings are consistent with several of the other studies. For instance, Study by Al-Malack found a steady increase in lead concentration over time, with lead levels reaching 0.78 mg/L after 48 h of exposure. Similarly, Study by Koh observed that lead extraction generally continued to increase with successive extractions, although the rate of increase diminished over time. For example, the study showed that the rate of extraction decreased after six or seven extractions.

The findings from this study, along with reported studies, indicate that higher temperatures and longer exposure durations can synergistically enhance the leachability of lead from uPVC pipes into drinking water. In this study, the mean concentration of lead in drinking water on day 2 was 98.78 µg/L, increasing by 44.2 % and 47.6 % after 5 and 10 days, respectively. Additionally, the variability in the results is evident, as the standard deviation for the uPVC 1, uPVC 2, and uPVC 3 pipes after 10 days is ± 39.33 µg/L, which is the highest among all conditions.

However, some studies reported different patterns. Study by Wong (1988), while lead leaching generally increased over time, the presence of certain extractants like HPO₄^2- resulted in a decrease in lead extraction rates at higher temperatures. This indicates that the interaction between time, temperature, and extractants can be complex. For instance, the study found that the lead concentration was lower at 45 °C compared to 27 °C when HPO₄^2- was used as an extractant.

The differences in results are attributed to the varying experimental designs, types of extractants used, and specific formulations of the uPVC pipes. For instance, this study shows that the type of uPVC pipe significantly influences lead leaching. uPVC2 consistently exhibited the highest lead concentrations at all time points and temperatures, with a maximum of 276 µg/L at 50 °C after 10 days. This suggests that the chemical composition and manufacturing process of the pipes play a crucial role in lead release.

These findings are corroborated by several other studies. For instance, Koh's Study found that pipes extruded at higher temperatures (190 °C) had lower lead leaching rates due to more uniform lead distribution. Similarly, Wong's Study (1990) reported that pipes extruded at 190 °C consistently exhibited lower lead extraction rates compared to those extruded at 170 °C or 180 °C. Specifically, the study showed that the lead concentration was significantly lower for pipes extruded at 190 °C, highlighting the importance of manufacturing processes.

Based on the obtained results, temperature, time, and different uPVC manufacturing processes significantly influence the leachability of lead from the pipes into drinking water. However, temperature exhibits the most pronounced effect.

Conclusion

Reducing the migration of lead from uPVC pipes into drinking water is a critical issue that requires immediate attention. The core findings of this study emphasize the significant roles of temperature and time in accelerating lead leaching from uPVC pipes. By employing a dual-method approach that combines ICP-OES for precise quantification and SEM-EDX for detailed elemental mapping, this research provides a more comprehensive and accurate analysis of lead presence and distribution compared to previous studies. The results demonstrate that higher temperatures and longer exposure times significantly increase lead release, as evidenced by uPVC pipes, which exhibited the highest lead concentrations. These findings suggest that controlling the temperature of drinking water and using pipes with optimized formulations can help mitigate lead contamination.

Several strategies can be employed to reduce lead migration, including the adoption of lead-free uPVC pipes or alternative materials with reduced lead content should be prioritized. This approach can significantly lower the risk of lead contamination. Additionally, maintaining the temperature of water within a safe range can minimize lead leaching. However, it is important to note that these measures should be implemented in conjunction with ongoing research to fully understand the mechanisms behind lead migration from uPVC pipes. This will allow for the development of more effective and long-term solutions to ensure the safety of our drinking water.

The findings of this study contribute significantly to the field by providing a systematic and comprehensive analysis of the factors influencing lead leaching from uPVC pipes. The use of controlled experimental conditions and consistent pipe types enhances the reliability of the results and provides a clear understanding of the influence of temperature, time, and pipe type on lead release. These insights can inform future research and guide the development of strategies to mitigate lead contamination in drinking water.

Future research should focus on optimizing the manufacturing processes of uPVC pipes to minimize lead content and enhance their resistance to environmental factors. Addressing these issues is crucial for ensuring the safety and quality of drinking water for future generations. It is also important to consider the long-term effects of lead leaching from uPVC pipes. While this study focused on a 10-day period, understanding the cumulative impact of lead migration over weeks or months is essential for assessing the safety of drinking water. Long-term studies can provide valuable insights into the durability and safety of uPVC pipes and help develop guidelines for their use in various environments.