From e-waste to living space: Flame retardants contaminating household items add to concern about plastic recycling

Table of Contents

Overall Summary

Study Background and Main Findings

This study investigated the presence of flame retardants (FRs) in black plastic household products, finding that 85% of the 20 analyzed products contained FRs, with concentrations up to 22,800 mg/kg. A strong correlation (R^2 = 0.91, p < 0.01) was found between bromine levels measured by XRF and total bromine content in BFRs measured by GC-MS, validating XRF as a screening tool. Notably, products made from ABS and HIPS plastics, commonly used in electronics, had significantly higher FR levels, with a median concentration of 4600 mg/kg compared to 150 mg/kg in other polymer types.

Research Impact and Future Directions

The study convincingly demonstrates a correlation between the use of specific polymers (ABS and HIPS) in black plastic household products and higher concentrations of flame retardants (FRs). The strong correlation between XRF and GC-MS measurements supports the use of XRF as a rapid screening tool for BFR contamination. However, the study stops short of establishing a direct causal link between e-waste recycling and FR contamination in these products.

The practical utility of the findings is significant, highlighting a previously under-recognized pathway for human exposure to potentially harmful chemicals. The study effectively places its findings within the context of existing research, acknowledging the limitations of current regulations and the need for greater transparency in the supply chain.

While the study provides valuable insights, it should offer more concrete guidance on mitigating the identified risks. Specific policy recommendations, such as mandatory labeling of FR content and stricter regulations on e-waste recycling, would enhance the paper's impact. The study also acknowledges uncertainties related to the lack of certified reference materials for some FRs.

Critical unanswered questions remain, particularly regarding the precise mechanisms of contamination and the long-term health effects of exposure to the detected FR levels. While the limited sample size and geographic focus are acknowledged, these limitations do not fundamentally undermine the study's conclusions. However, further research with larger, more diverse samples is needed to confirm the generalizability of the findings and to investigate the potential health impacts more thoroughly.

Critical Analysis and Recommendations

Clear motivation and research question (written-content)
The abstract clearly states the motivation for the study, highlighting the health concerns associated with flame retardants and the potential for unintentional exposure through recycled plastics. This effectively establishes the significance of the research and its relevance to public health.
Section: Abstract
Quantify the "lack of transparency" and "limited restrictions" (written-content)
The abstract mentions "lack of transparency" and "limited restrictions" regarding FR use but fails to quantify these issues. Providing specific numbers or examples would strengthen the paper by allowing readers to quickly grasp the severity of the issue and the need for the study.
Section: Abstract
Clear context and motivation (written-content)
The introduction clearly establishes the context and motivation for the study by highlighting the widespread presence of flame retardants (FRs) in the environment and the associated human exposure concerns. This effectively sets the stage for the research and emphasizes its importance.
Section: Introduction
Explicitly state the knowledge gap (written-content)
The introduction lacks a clear statement of the specific knowledge gap this study aims to fill. Explicitly stating what is currently unknown or understudied about FR contamination in household products would strengthen the rationale for the study and highlight its potential contribution to the field.
Section: Introduction
Clear rationale for analyte selection (written-content)
The methods section provides a clear rationale for the selection of analytes, focusing on FRs previously detected in electronics and those marketed for use in electronics. This targeted approach ensures relevance to the study's hypothesis and maximizes the potential for meaningful findings.
Section: Methods
Elaborate on XRF calibration procedures (written-content)
The methods section lacks a detailed description of the XRF calibration process, including the specific standards used and the frequency of calibration checks. Providing this information is essential for ensuring the accuracy of the bromine measurements and would enhance the paper's reproducibility.
Section: Methods
Clear presentation of key findings (written-content)
The results section effectively presents the key findings, including the prevalence of FRs, the types of FRs detected, and the relationship between polymer type and FR levels. The data is presented clearly in tables and figures, making it easy to understand the main takeaways.
Section: Results and discussion
Discuss potential contamination sources and pathways (written-content)
The discussion primarily focuses on the presence and levels of FRs but lacks a deeper exploration of potential contamination sources and pathways. Adding a more in-depth discussion of these aspects would provide a more comprehensive understanding of the problem and inform potential solutions.
Section: Results and discussion
Provide specific policy recommendations (written-content)
The policy implications section lacks concrete, actionable recommendations for policy changes or regulatory actions. Providing specific recommendations would strengthen the paper by offering clear guidance for policymakers and stakeholders on how to mitigate the risks associated with FR contamination.
Section: Policy implications
Indication of Correlation Strength (graphical-figure)
Figure 2 includes the R2 value (0.91), providing a quantitative measure of the correlation strength between XRF Br levels and total Br content in BFRs. This is crucial for validating the use of XRF as a screening tool.
Section: Results and discussion

Section Analysis

Abstract

Key Aspects

Strengths

Suggestions for Improvement

Introduction

Key Aspects

Strengths

Suggestions for Improvement

Methods

Key Aspects

Strengths

Suggestions for Improvement

Non-Text Elements

Table 1 Sample summary.
First Reference in Text
A total of 203 black plastic products (food serviceware, n = 28; hair accessories, n = 30; kitchen utensils, n = 109; toys, n = 36) were pur- chased from online retailers and local stores in and around Seattle, USA from 2020 to 2022 (Table 1).
Description
  • Purpose of Table 1: Table 1 provides a summary of the samples that were collected and analyzed in this study. It breaks down the total number of products tested into different categories, showing how many of each type were purchased from different sources. This gives us a quick overview of the data set.
  • Table Structure: The table is organized into three columns: "Product Category," "# of Products Purchased from a Local Retailer," "# of Products Purchased from a Chain Retailer," and "% of Products >50 mg/kg Br." Each row represents a different category of product, such as "Food Serviceware" or "Toys."
  • Product Categories and Sample Sizes: The table lists four product categories: Food Serviceware, Hair Accessories, Kitchen Utensils, and Toys. For each category, the table shows the number of products purchased from two different types of retailers: local retailers and chain retailers. "Local retailers" likely refers to small, independent stores, while "chain retailers" refers to larger, national or international companies. The "n" in the reference text refers to the sample size, or the number of items in each category. For example, "n = 28" for food serviceware means that 28 food serviceware items were included in the study.
  • Bromine Contamination Levels: The last column, "% of Products >50 mg/kg Br," indicates the percentage of products in each category that had bromine (Br) levels greater than 50 milligrams per kilogram (mg/kg). Milligrams per kilogram is a unit of measurement that tells us how much of a substance is present in a given weight of material, similar to parts per million (ppm) as discussed before. This column provides a quick measure of the extent of potential contamination in each product category. The researchers are interested in bromine because it is a common component of certain flame retardant chemicals.
Scientific Validity
  • Sample Representativeness: The table provides a clear breakdown of the sample by product category and retailer type, which is important for assessing the generalizability of the findings. However, the sample is limited to products purchased in and around Seattle, USA, which may not be representative of products sold in other regions or countries. Additionally, the table does not specify the criteria used for selecting specific retailers or products within each category, which could introduce selection bias.
  • Sample Size Adequacy: The sample sizes for each product category are relatively small, particularly for food serviceware (n=28) and toys (n=36). While these sample sizes may be sufficient for an exploratory study, larger sample sizes would be needed to draw more robust conclusions about the prevalence of flame retardant contamination in different product categories.
  • Relevance to Research Question: The table directly relates to the research question by providing an overview of the samples analyzed in the study. The information presented in the table is essential for understanding the scope and limitations of the study.
Communication
  • Clarity of Presentation: The table is well-organized and easy to understand. The column headings are clear and concise, and the use of bold font for the product categories makes the table easy to read.
  • Completeness of Information: The table provides a good overview of the sample, but it could be improved by including additional information, such as the total number of products purchased from each retailer type and the specific criteria used for selecting retailers and products. Additionally, the table could include information on the specific types of local and chain retailers included in the study (e.g., names of stores or types of businesses).
  • Conciseness: The table is concise and presents the information in a straightforward manner. The use of abbreviations (e.g., "#" for "number" and "Br" for "bromine") is appropriate and does not detract from the table's readability.

Results and discussion

Key Aspects

Strengths

Suggestions for Improvement

Non-Text Elements

Fig. 1. Examples of products containing >50 ppm Br as determined by XRF Fig....
Full Caption

Fig. 1. Examples of products containing >50 ppm Br as determined by XRF Fig. 1aPirate Coin Medallion Beads Fig. 1b. Tabletop Pool Fig. 1c. Slotted Turner Fig. 1dSushi Tray.

First Reference in Text
Examples of products containing >50 ppm Br as determined by XRF are shown in Fig. 1.
Description
  • Purpose of Figure 1: Figure 1 is meant to show examples of everyday items that were found to have more than 50 parts per million (ppm) of Bromine (Br). "Parts per million" is a way to measure very small amounts of a substance within a larger mixture, like a tiny drop in a big bucket. In this research, it refers to how much bromine is present within the plastic of each product. 50 ppm is a threshold value chosen by the authors that represents a significant amount of bromine. XRF, which stands for X-ray fluorescence, is the method used to measure this. XRF is a technique that uses X-rays to determine the chemical elements present in a sample. Imagine shining a special light on something that makes it glow in a way that tells you what it's made of—that's similar to how XRF works.
  • Content of Figure 1: The figure contains four images (labelled 1a, 1b, 1c, and 1d) of plastic products. Image 1a displays an image of a product called "Pirate Coin Medallion Beads". Image 1b displays an image of a product called "Tabletop Pool". Image 1c displays an image of a product called a "Slotted Turner", which is a type of kitchen utensil. Image 1d displays an image of a product called a "Sushi Tray", used for food service.
  • Context of Figure 1: This figure is part of a larger study investigating whether harmful flame retardant chemicals used in electronic waste are contaminating everyday plastic items. Flame retardants are chemicals added to products to slow down or prevent fires. Bromine is a chemical element often found in these flame retardants. The researchers are concerned because these chemicals might be getting into new products through recycled plastic, potentially exposing people to harmful substances.
Scientific Validity
  • Relevance to Research Question: The figure directly relates to the study's objective of identifying flame retardant contamination in household items. By visually presenting examples of products with significant bromine levels, it provides tangible evidence supporting the claim that such contamination exists.
  • Methodological Transparency: The caption correctly identifies XRF as the method used for bromine measurement. This is crucial for scientific validity as it allows other researchers to understand and potentially replicate the analysis. However, the figure itself does not provide details on the specific XRF parameters used or the calibration procedures, which would further enhance transparency.
  • Selection Bias: While the caption states that these are "examples," it's unclear how these specific products were chosen for display. Were they the items with the highest bromine levels, or were they selected based on other criteria? Clarifying the selection process is essential to avoid potential bias and ensure the figure accurately represents the overall findings.
Communication
  • Clarity of Caption: The caption is relatively clear in stating the figure's purpose and the method used. However, it could be improved by explicitly stating that the images are photographs of the products and briefly explaining why a 50 ppm threshold was used.
  • Visual Clarity: The images are simple and clearly show the products. The labels (1a, 1b, 1c, 1d) are distinct and easy to read. The images are not too small.
  • Completeness of Information: The figure would be more informative if it included the specific bromine concentration measured for each product. This would provide a better sense of the range of contamination levels found. Additionally, indicating the product's material (e.g., type of plastic) would further enhance the figure's informational value.
Fig. 2. Correlation between XRF Br levels and total Br content in BFRs measured.
First Reference in Text
Linear regression assessing the relationship between XRF Br content and the sum of Br content in BFRs detected found a strong and signifi- cant association between the two variables (p < 0.01, R2 = 0.91) (Fig. 2).
Description
  • Purpose of Figure 2: Figure 2 is a scatter plot that shows the relationship between two different ways of measuring bromine (Br) levels in the plastic products. It aims to see if the measurements obtained using a faster, simpler method (XRF) are consistent with those obtained using a more complex, time-consuming method that measures the total bromine content in specific brominated flame retardants (BFRs). XRF, or X-ray fluorescence, is like shining a special light on the plastic to get a quick estimate of its bromine content. Measuring total Br content in BFRs is a more detailed chemical analysis that identifies and quantifies specific bromine-containing compounds. BFRs are the target chemicals of concern in this research. The plot is used to validate whether the quicker XRF method is a reliable indicator of the actual total bromine levels from these harmful flame retardants.
  • Axes of the Plot: The horizontal axis (X-axis) represents the bromine levels measured by XRF, in parts per million (ppm). The vertical axis (Y-axis) represents the total bromine content in the measured BFRs, also in milligrams per kilogram (mg/kg). Each dot on the plot represents one plastic product, and its position is determined by its XRF bromine level (X-axis) and its total bromine content from BFRs (Y-axis).
  • Correlation and R2 Value: The plot shows how the two measurements relate to each other. A correlation is a statistical measure that describes the extent to which two variables change together. If the dots generally trend upwards from left to right, it suggests a positive correlation, meaning that higher XRF bromine levels tend to correspond to higher total bromine content in BFRs. The R2 value of 0.91, mentioned in the reference text, is a number between 0 and 1 that indicates how well the XRF measurements predict the total bromine content in BFRs. A value of 0.91 is very high, suggesting a strong relationship, meaning the XRF measurements are a good indicator of the actual total bromine levels from BFRs. The closer R2 is to 1, the better the prediction. A p-value less than 0.01 indicates that this relationship is statistically significant, which means it's unlikely to have occurred by chance and that there is a real association between the two measurements.
  • Logarithmic Scale: The plot uses a logarithmic scale for both axes. This means that instead of equal intervals representing equal amounts (like on a ruler), equal intervals represent equal ratios. For example, the distance between 1 and 10 is the same as the distance between 10 and 100. This is useful when dealing with data that spans a wide range of values, as is the case here, because it allows us to see the relationship more clearly across the entire range.
Scientific Validity
  • Appropriateness of Statistical Analysis: The use of linear regression to assess the correlation between XRF Br levels and total Br content in BFRs is appropriate given the research question. The reported p-value and R2 value provide quantitative measures of the strength and significance of the association.
  • Validation of XRF Method: The strong correlation observed (R2 = 0.91) provides evidence that XRF can be a reliable screening tool for estimating total Br content in BFRs, which is valuable for rapid assessment in larger sample sets. However, it's important to note that the figure does not provide information about the specific linear regression equation, which would be necessary for precise quantitative predictions.
  • Consideration of Outliers: The scatter plot reveals a few data points that deviate somewhat from the general trend. These outliers should be investigated further to determine whether they represent measurement errors, unique samples, or limitations of the XRF method under certain conditions. Their influence on the regression analysis should also be assessed.
Communication
  • Clarity of Caption: The caption clearly states the purpose of the figure and the variables being compared. However, it could be improved by briefly mentioning that the figure is a scatter plot and that a logarithmic scale is used.
  • Labeling of Axes: The axes are clearly labeled with the measured variables and their units (ppm for XRF Br levels and mg/kg for total Br content in measured BFRs). The use of a logarithmic scale is indicated on each axis, which is essential for proper interpretation of the data. However, the font size of the axis labels could be slightly increased for better readability.
  • Indication of Correlation Strength: The inclusion of the R2 value (0.91) in the plot is crucial as it provides a quantitative measure of the correlation strength. It would be beneficial to also include the p-value directly on the plot for a more complete presentation of the statistical results.
  • Visual Representation of Data: The scatter plot effectively visualizes the relationship between the two variables. The use of a logarithmic scale allows for a clear representation of data points across a wide range of values. However, adding a trend line to the plot would further enhance the visualization of the correlation.
Fig. 3. Products are labeled with their sample numbers (S1, S2...S20), which...
Full Caption

Fig. 3. Products are labeled with their sample numbers (S1, S2...S20), which can be referenced for more information on FR results in Tables S5 and S6.

First Reference in Text
Analysis for polymer type using FTIR of the 20 products that screened >50 ppm Br found that ABS and HIPS/PS were the dominant polymers (Fig. 2).
Description
  • Purpose of Figure 3: Figure 3 is a bar graph that shows the total concentration of flame retardants (FRs) found in 20 different products. Flame retardants are chemicals added to materials to slow down or prevent fire. The purpose of this figure is to illustrate which types of plastic polymers contained in these products have higher amounts of these potentially harmful chemicals. It also aims to connect this information with the specific products tested, allowing readers to see which items had higher or lower levels of these chemicals.
  • Structure of the Graph: The graph has a vertical axis (Y-axis) that represents the total concentration of flame retardants in milligrams per kilogram (mg/kg), which is a unit of measurement for how much of a substance is present in a given weight of material. The horizontal axis (X-axis) lists different product samples, categorized by their polymer type. Polymers are large molecules that make up plastics, and different types of polymers have different properties. Each product is represented by a bar, and the height of the bar indicates the total concentration of flame retardants found in that product. Each product is also labeled with a sample number (S1, S2, etc.) for easy reference.
  • Polymer Types: The graph shows several different polymer types, including ABS (acrylonitrile butadiene styrene), which is a common thermoplastic polymer known for its toughness and impact resistance, often used in electronic housings and toys; HIPS/PS (high-impact polystyrene/polystyrene), which is another common plastic often used for packaging and containers; Polypropylene, which is a versatile polymer used in a wide range of applications, including food containers and packaging; Poly(propylene:ethylene), which is a copolymer that combines properties of both polypropylene and ethylene; and Polyamide/nylon, which is a strong and durable synthetic polymer often used in textiles and engineering applications. The key at the bottom of the graph indicates which product categories are associated with each bar color. FTIR (Fourier-transform infrared spectroscopy) is an analytical technique used to identify these polymer types. It works by shining infrared light on a sample and measuring how much light is absorbed at different wavelengths. The absorption pattern is like a fingerprint that can be used to identify the material.
  • Connection to Supplementary Tables: The caption mentions that more information about the flame retardant (FR) results for each product can be found in Tables S5 and S6 in the supplementary materials. These tables likely provide detailed data on the specific types and concentrations of flame retardants found in each product, allowing for a more in-depth analysis.
Scientific Validity
  • Relevance to Research Question: This figure directly addresses the research question of whether certain polymer types are associated with higher levels of flame retardant contamination. By categorizing products based on their polymer type and showing the corresponding FR concentrations, it provides evidence for potential links between polymer type and contamination levels.
  • Methodological Soundness: The use of FTIR to determine polymer type is a standard and reliable method in materials science. The figure's validity is strengthened by the fact that it is based on quantitative measurements of FR concentrations, although the specific analytical methods used to obtain these measurements are not detailed in the caption or figure itself.
  • Sample Size and Representation: The figure presents data for 20 products, which is a relatively small sample size. While this may be sufficient for preliminary investigations, a larger sample size would be needed to draw more definitive conclusions about the relationship between polymer type and FR contamination. Additionally, the figure's caption does not provide information on how these 20 products were selected from the larger pool of 203 screened products, which could introduce selection bias.
Communication
  • Clarity of Caption: The caption clearly states that the figure shows products labeled with sample numbers and that more information can be found in supplementary tables. However, it could be improved by explicitly stating that the figure is a bar graph and briefly explaining what the height of each bar represents. It also incorrectly refers to "Fig. 2" in the reference text when it should be "Fig. 3".
  • Labeling and Organization: The figure is well-organized, with clear labels for the axes and a key for the different product categories. The use of sample numbers (S1, S2, etc.) allows for easy cross-referencing with the supplementary tables. However, the font size of the axis labels and the key could be increased for better readability. The specific polymer type for each product is abbreviated on the x-axis, which may be difficult for readers unfamiliar with these abbreviations. It would be helpful to spell out these names, at least in a footnote or a separate table.
  • Visual Presentation: The bar graph format is appropriate for visualizing the data and comparing FR concentrations across different products and polymer types. The use of color to distinguish product categories is helpful. However, the figure could be made more visually appealing and informative by ordering the bars from highest to lowest FR concentration, which would make it easier to identify trends and patterns.
  • Accessibility of Information: The figure provides a good overview of the relationship between polymer type and FR concentration. However, the reliance on sample numbers and supplementary tables to access detailed information about each product may make it difficult for readers to fully understand the data without consulting the supplementary materials. Including the product names or brief descriptions directly on the figure or in a separate table would improve its stand-alone interpretability.
Table 2 Br levels detected by XRF.
First Reference in Text
XRF screening of the 203 products identified 20 products with >50 ppm Br, ranging up to 18,600 ppm (Table 2).
Description
  • Purpose of Table 2: Table 2 shows the levels of bromine (Br) found in 20 different products. These products were selected because they had more than 50 parts per million (ppm) of bromine, as measured by a technique called X-ray fluorescence (XRF). XRF is like shining a special light on a material to figure out what it's made of. In this case, it was used to measure how much bromine is present in each product. The table lists these 20 products and their corresponding bromine levels, providing a more detailed look at the products with the highest bromine concentrations.
  • Table Structure: The table has four columns: "Product Name," "Product Category," "Br (ppm)," and "Sb (ppm)ª." Each row represents one of the 20 products. The "Product Name" column gives a brief description of the product. The "Product Category" column tells us what type of product it is, such as "Food Serviceware," "Toys," or "Kitchen Utensils." The "Br (ppm)" column shows the bromine level in parts per million, and the "Sb (ppm)ª" column shows the level of antimony (Sb), another chemical element, also in parts per million. The footnote "ª ND = not detected" indicates that if a cell in the "Sb (ppm)" column says "ND," it means that no antimony was found in that product using the XRF method.
  • Bromine and Antimony Levels: Bromine (Br) is a chemical element that is often found in certain flame retardants. Antimony (Sb) is another element that is sometimes used along with bromine in flame retardants to enhance their effectiveness. The table shows the levels of both elements in each product. The higher the number in the "Br (ppm)" column, the more bromine was detected in that product. The presence of antimony could provide further evidence that flame retardants are present.
  • Focus on High-Bromine Products: The table focuses on the 20 products with the highest bromine levels out of the 203 products that were initially screened. This suggests that these products are of particular interest because they are more likely to contain significant amounts of brominated flame retardants. By presenting the data for these specific products, the table highlights the extent of potential contamination in items that people might commonly use.
Scientific Validity
  • Relevance to Research Question: This table directly addresses the research question by identifying products with high bromine levels, which are indicative of potential flame retardant contamination. The use of XRF to measure bromine levels is appropriate given the study's objective of screening for the presence of brominated flame retardants.
  • Methodological Transparency: The table clearly states that XRF was used for bromine detection, which is important for scientific reproducibility. However, the caption and table do not provide details on the specific XRF instrument used, the calibration procedures, or the quality control measures implemented. Providing this information in the methods section or supplementary materials would enhance the study's transparency.
  • Selection Criteria: The table focuses on the 20 products with bromine levels greater than 50 ppm, which is a reasonable threshold for identifying potentially contaminated products. However, it is important to note that this threshold is somewhat arbitrary, and products with lower bromine levels may still contain flame retardants. Additionally, the table does not explain why these specific 20 products were chosen for further analysis beyond having >50 ppm Br, which could introduce selection bias.
  • Use of Antimony as a Synergist Indicator: The inclusion of antimony (Sb) levels is relevant as antimony is often used as a synergist with brominated flame retardants. The detection of both elements in some products strengthens the evidence for the presence of flame retardants. However, the absence of antimony does not rule out the presence of brominated flame retardants, as not all formulations use antimony as a synergist.
Communication
  • Clarity of Caption: The caption clearly states the purpose of the table and the method used for bromine detection. However, it could be improved by briefly explaining why products with >50 ppm Br were selected and by mentioning that antimony levels are also included in the table.
  • Table Organization and Readability: The table is well-organized and easy to read. The column headings are clear and informative, and the use of footnotes to explain abbreviations is helpful. However, the font size could be slightly increased to improve readability.
  • Product Identification: The use of product names and categories is helpful for identifying the specific items with high bromine levels. However, some of the product names are somewhat vague (e.g., "Peeler" or "Slotted Spoon"). Providing more specific product descriptions or including product numbers that correspond to a more detailed list in the supplementary materials would enhance the table's informational value.
  • Presentation of Quantitative Data: The table effectively presents the quantitative data for bromine and antimony levels. The use of "ND" to indicate non-detects is appropriate. However, it would be helpful to include the limit of detection (LOD) for both bromine and antimony in the table's footnote or methods section. This would provide a better understanding of the sensitivity of the XRF measurements and the meaning of "ND" values.
Table 3 Summary of FRs detected.
First Reference in Text
This included BFRS TBBPA (detected in 75% of samples), 2,4,6-ΤΒΡ (70%), BDE-209 (70%), DBDPE (60%), and TTBP-TAZ (50%), and OPFRS BDP (60%), RDP (60%), and TPHP (55%) (see Table 3 for a summary of the results).
Description
  • Purpose of Table 3: Table 3 summarizes the different types of flame retardants (FRs) that were found in the 20 products analyzed. Flame retardants are chemicals added to materials to slow down or prevent fires. This table shows how often each type of flame retardant was detected and in what concentrations. It provides a summary of the main findings regarding the specific flame retardants identified in the products.
  • Table Structure: The table has five columns: "FRs," "Full Chemical Name," "Detection Frequency (n = 20)," "Median (mg/kg)," and "Range (mg/kg)." Each row represents a different flame retardant. The "FRs" column lists the abbreviated name of each flame retardant, while the "Full Chemical Name" column provides its complete chemical name. "Detection Frequency" indicates how often each flame retardant was found in the 20 samples, expressed as a percentage. "Median (mg/kg)" shows the median concentration of each flame retardant in milligrams per kilogram, which is a measure of the amount of the chemical found in a given weight of the product. The median represents the middle value when all the concentrations are arranged in order. "Range (mg/kg)" shows the lowest and highest concentrations found for each flame retardant.
  • Types of Flame Retardants: The table lists several different types of flame retardants, including both brominated flame retardants (BFRs) and organophosphate flame retardants (OPFRs). BFRs are flame retardants that contain bromine, while OPFRs are flame retardants that contain phosphorus. Some common BFRs listed in the table include TBBPA (Tetrabromobisphenol A), BDE-209 (Decabromodiphenyl ether), and DBDPE (Decabromodiphenyl ethane). Some common OPFRs listed include RDP (Resorcinol bis(diphenylphosphate)), BDP (Bisphenol-A bis(diphenyl phosphate)), and TPHP (Triphenyl phosphate). The table also includes 2,4,6-TBP (2,4,6-Tribromophenol) which is a common degradation product or impurity associated with other BFRs. These abbreviations can be difficult to understand without a chemistry background, but the table provides the full chemical names for those who are interested.
  • Concentration Levels: The table provides information on both the frequency and the concentration levels of each flame retardant. The "Detection Frequency" column tells us how common each flame retardant was among the 20 samples. The "Median" and "Range" columns tell us how much of each flame retardant was typically present and what the lowest and highest amounts were. This helps us understand not only which flame retardants were present but also in what quantities. For example, a flame retardant with a high detection frequency and a high median concentration would be considered more prevalent and potentially more concerning than a flame retardant with a low detection frequency and a low median concentration.
Scientific Validity
  • Relevance to Research Question: This table directly addresses the research question by providing a comprehensive summary of the flame retardants detected in the analyzed products. The data presented in the table are essential for understanding the prevalence and levels of different flame retardants in common household items.
  • Methodological Transparency: The table provides a clear overview of the analytical results, but it does not include details on the analytical methods used to identify and quantify the flame retardants. Providing this information (e.g., type of mass spectrometry, sample preparation procedures, quality control measures) in the methods section or supplementary materials is crucial for scientific rigor and reproducibility.
  • Appropriateness of Summary Statistics: The use of detection frequency, median, and range is appropriate for summarizing the data. However, given the relatively small sample size (n=20), reporting the interquartile range (IQR) in addition to the median would provide a more robust measure of the central tendency and variability of the data, especially for non-normally distributed data.
  • Completeness of Data: The table includes data for 12 different flame retardants. The reference text highlights that these are the most frequently detected compounds, but it does not state whether any other FRs were analyzed but not detected. Providing a complete list of all analyzed FRs, including those not detected, in the supplementary materials would enhance the transparency and completeness of the data.
Communication
  • Clarity of Caption: The caption clearly states the purpose of the table, which is to summarize the flame retardants detected. However, it could be improved by briefly mentioning that the table includes both BFRs and OPFRs.
  • Table Organization and Readability: The table is well-organized and easy to read. The column headings are clear and informative, and the use of abbreviations for the flame retardants is appropriate given the space constraints. However, the font size could be slightly increased to improve readability.
  • Accessibility of Information: The table provides both the abbreviated and full chemical names of the flame retardants, which is helpful for readers who may not be familiar with all the abbreviations. However, the table could be made more accessible by including a brief description of each flame retardant's common uses or sources in a footnote or separate table. There is a typo in the reference text: "2,4,6-ΤΒΡ" is written as "2,4,6-ТВР".
  • Presentation of Quantitative Data: The table effectively presents the quantitative data on detection frequency, median, and range. The use of consistent units (mg/kg) for concentration is appropriate. However, as mentioned earlier, including the interquartile range (IQR) would provide a more complete picture of the data distribution.

Policy implications

Key Aspects

Strengths

Suggestions for Improvement

Conclusion

Key Aspects

Strengths

Suggestions for Improvement

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