3.1. Regulatory status
In the EU, BPA is classified as a substance that adversely affects reproduction, irritates the respiratory tract, causes serious eye damage, and can trigger skin allergies. Companies supplying BPA to the EU must classify and label it, and mixtures containing it, according to the harmonised classification. Germany has proposed additional harmonised classifications that include the risk to the aquatic environment (acute and chronic). The Committee for Risk Assessment (RAC) that operates within the framework of the ECHA has supported this proposal. Since March 2018, the use of BPA as a stand-alone substance and in mixtures intended for consumer use has been restricted in the EU. The use of BPA in thermal paper was further restricted in 2020. Henceforth, thermal paper containing 0.02% or more BPA is no longer allowed on the EU market. France and Sweden have proposed to restrict over 1000 skin-sensitising chemicals in clothing, footwear and other articles with similar skin contact, including BPA. The RAC has supported this proposal, and a final decision is to be taken by the Commission together with the Member States (Bisfenol A - ECHA). In the EU, BPA can be used in food contact materials, but only 0.05 mg/kg is allowed to leach from the materials into the food. Of note, BPA has been banned in infant bottles throughout the EU since June 2011. Later, in 2018, it was also banned from plastic bottles and packaging containing food for babies and children under 3 years of age. Moreover, France has banned BPA in all food packaging, containers and utensils. The EFSA has also limited the amount of BPA that can leach from toys for children up to 3 years of age, and from toys intended to be placed in a child's mouth, to 0.04 mg/L (Scientific Opinion on the Risks to Public Health Related to the Presence of Bisphenol A (BPA) in Foodstuffs, 2015). In its draft re-evaluation in December 2021, the EFSA proposed lowering the TDI from 4 µg/kg bw/day to 0.04 ng/kg bw/day (Bisphenol A, EFSA 2021). The most recent ECHA market survey on the use of BPA and other thermal paper developers confirmed that paper manufacturers continue to substitute BPA with bisphenol S (BPS). Accordingly, in 2019, 187 kilotonnes of BPS-based thermal paper were placed on the EU market, and it is expected that by 2022, 61% (307 kilotonnes) of all of the thermal paper in the EU will be BPS based. The widespread use of BPS in thermal paper also constitutes a cause for concern, as BPS is believed to also affect the human reproductive and endocrine systems. To this end, Belgium has proposed to harmonise the classification and labelling of BPS as toxic for reproduction (Bisphenol S has replaced bisphenol A in thermal paper - All News - ECHA). Much less information on the restrictions of BPA is available for the USA, however. Since 2012, BPA has no longer been allowed in polycarbonate resins for baby bottles and ‘sippy’ cups. The FDA also banned BPA-based epoxy resins as coatings in packaging for infant formula (Bisphenol A (BPA): Use in food contact application | FDA). Moreoever, BPA should not be present in cell phone cases in concentrations over 3 ppm, and thermal paper at over 10 ppm. Other countries have restricted the use of BPA in food contact products (i.e., Argentina, Australia [voluntary phase out], Brazil, Canada, China, Costa Rica, Ecuador, Japan, Malaysia, South Africa, South Korea, Taiwan, Turkey), especially in those for infant use (BPA Bans and restrictions in food contact materials | SGS).
3.2. Major sources
Bisphenols are composed of two phenol moeties, and several prominent examples are shown in Figure 1. They are generally used in the manufacture of polycarbonate plastics and epoxy resins. Synthetic polymers of BPA are characterised by good mechanical properties, low moisture absorption and thermal stability. Therefore, they are used in various products such as water pipes, food containers, bottles, toys, nipples, medical devices, dental products, electronic devices and CD/DVD disks (Michałowicz, 2014). The annual production of BPA in the USA ranged from 940000 tonnes to 1030000 tonnes from 2000 to 2019, but the Asia-Pacific region dominates the bisphenols market (Bisphenol A production USA 2019). As well as polycarbonate plastics and epoxy resins, BPA is used in the paper industry as a colour developer in thermal paper (Geens et al., 2012). In the thermal paper used for receipts, BPA is the most frequent of all the bisphenols, at concentrations from 5.6 to 30.4 mg/g, while its alternative BPS has been reported at lower concentrations, from 3.3 to 13.2 mg/g (Goldinger et al., 2015). However, since January 2020, thermal paper containing more than 0.02% BPA is no longer allowed on the EU market (Bisfenol A - ECHA).
As indicated, BPA is still the most widely used among the bisphenols, but due to increasing restrictions, the use of other bisphenols has increased, and especially of BPS. Since the discovery of BPA-related adverse effects on the kidneys and mammary glands, the EU has temporarily reduced the daily intake of BPA from 50 to 4 mg/kg body weight/day, and many countries have prohibited its use in children's products. As a result, many companies have switched to using other bisphenol analogues, such as BPS and bisphenol F (BPF). Similar to BPA, BPS is used in polycarbonates, epoxies, thermal paper, and certain consumer products that can thus be labelled as ‘BPA-free’. It is also used in personal care products and 13 categories of food (Liao & Kannan, 2013; Zheng et al., 2018). The European consumption of BPS is estimated to be between 1000 and 10000 tonnes per year (Lehmler et al., 2018).
3.3. Level of environmental contamination
The widespread use of bisphenols in everyday life has led to their occurrence in the environment. This has been confirmed for both WWTP influent and effluent water, as well as for surface waters, including rivers, lakes and seas, which has consequently resulted in contamination of the biota (e.g., accumulation in fish) (see Table 3).
Table 3
Occurrence of bisphenols in the environment.
Sample/Location
|
Bisphenol
|
Concentration
|
Reference
|
Effluent water from paper recycling plant (Japan)
|
BPA
|
up to 370 µg/L
|
(Fukazawa et al., 2001)
|
Influent water from WWTP (Romania)
|
BPS
|
1160-1688 ng/L
|
(Chiriac et al., 2021)
|
BPE
|
483-744 ng/L
|
BPA
|
6422-9140 ng/L
|
BPF, BPB, BPC
|
n.d.
|
Effluent water from WWTP (Romania)
|
BPA
|
6.32-73.6 ng/L
|
BPS, BPE, BPF, BPB, BPC
|
n.d.
|
Influent water from WWTP (Slovenia)
|
Sum of bisphenols
|
6.66 – 16.4 ng/L
|
(Česen et al., 2018)
|
River water near chemical industrial zone (China)
|
BPA
|
average: 415 ng/L
|
(Lan et al., 2019)
|
River water (Spain)
|
BPA
|
up to 817 ng/L
|
(Bolívar-Subirats et al., 2021)
|
River water (China)
|
BPS
|
up to 18.99 ng/L
|
(Yang et al., 2014b)
|
BPA
|
up to 74.58 ng/L
|
BPAF
|
up to 245.69 ng/L
|
River water (Romania)
|
BPS
|
6.15-8.23 ng/L
|
(Chiriac et al., 2021)
|
BPA
|
74.5-135 ng/L
|
BPE, BPF, BPB, BPC
|
n.d.
|
Influent water (Canada)
|
BPA
|
up to 1000 ng/L
|
(Muir et al., 2017)
|
Harbour water (Canada)
|
up to 10 ng/L
|
Surface water samples (Japan, China, Korea, India)
|
BPF
|
up to 2850 ng/L in Japan
|
(Yamazaki et al., 2015)
|
BPA
|
up to 1950 ng/L in India
|
BPS
|
up to 7200 ng/L in India
|
19-23 freshwater sites; 8-14 marine locations (Netherlands)
|
BPA
|
up to 21 µg/L
|
(Belfroid et al., 2002)
|
Surface sediments
(USA, Japan, Korea)
|
BPA
|
117 ng/g
|
(Liao et al., 2012b)
|
BPS
|
12.37 ng/g
|
BPF
|
69.7 ng/g
|
Others
|
2 ng/g or less
|
Sediment near chemical industrial zone (China)
|
BPA
|
average 521 ng/g dw
|
(Lan et al., 2019)
|
Sediment (China)
|
BPF
|
up to 30.17 ng/g
|
(Yang et al., 2014b)
|
BPA
|
up to 42.76 ng/g
|
BPAF
|
up to 2009.8 ng/g
|
Indoor dust (US, China, Japan, Korea)
|
BPA
|
1.6 µg/g
|
(Liao et al., 2012a)
|
BPS
|
0.36 µg/g
|
BPF
|
0.096 µg/g
|
Other
|
less than 1 ng/g
|
Indoor dust (China, Columbia, Greece, India, Japan, South Korea, Kuwait, Pakistan, Romania, Saudi Arabia, US, Vietnam)
|
BPA
|
1000 ng/g
|
(W. Wang et al., 2015)
|
BPF
|
1000 ng/g
|
BPS
|
220 ng/g
|
BPAF
|
3.1 ng/g
|
Others
|
less than 1 ng/g
|
Food
|
Bisphenols
|
4.38 ng/g
|
(Liao & Kannan, 2011)
|
Fish
|
BPA
|
liver: 2–75 ng/g
|
(Belfroid et al., 2002).
|
muscle: 1–11 ng/g
|
muscle: up to 59.3 ng/g
|
(Ademollo et al., 2018)
|
liver: up to 105.3 ng/g
|
liver: 36.2–51.4 ng/g
|
(Errico et al., 2017)
|
muscle: 18.8–84.8 ng/g
|
brain: 31–46 ng/g
|
(Ros et al., 2016)
|
muscle: 20–28 ng/g
|
liver: 49–97 ng/g
|
muscle: 16.2 ng/g
|
(Barboza et al., 2020)
|
BPB
|
muscle: 7.3 ng/g
|
Canned seafood
|
BFDGE
|
up to 4.2 µg/g
|
(Theobald et al., 2000).
|
n.d. not detected
Bisphenol A was detected in wastewater from a paper recycling plant in Japan at concentrations of up to 370 µg/L (Fukazawa et al., 2001). In contrast, a more recent study reported lower concentrations of bisphenols in influent water from a WWTP in Romania, as BPS (1160-1688 ng/L), bisphenol E (BPE; 483-744 ng/L) and BPA (6422-9140 ng/L). As expected, the concentrations were two to three orders of magnitude lower in the effluent water, where BPA ranged from 6.32 to 73.6 ng/L, while BPS was below the limit of quantification, and BPE was not detected (Chiriac et al., 2021). Similar concentrations of bisphenols were detected in influent wastewater in Slovenia (6.66-16.4 ng/L) (Česen et al., 2018). River samples generally contain lower concentrations of bisphenols than influent wastewater, with the exception of a river in China near a chemical industrial zone (mean BPA, 415 ng/L) (Lan et al., 2019) and in a river in Spain (bisphenols up to 817 ng/L) (Bolívar-Subirats et al., 2021). Samples from different rivers have been reported to contain individual bisphenols at maximum concentrations from 6.15 to 245.69 ng/L (Chiriac et al., 2021; Lan et al., 2019). In Canada, BPA has been reported for surface waters near WWTPs at up to 1000 ng/L, while in harbour waters, BPA levels were two orders of magnitude lower (up to 10 ng/L) (Muir et al., 2017). In Japan, surface waters have shown BPF at 2850 ng/L, and in India, BPA and BPS in surface waters were 1950 ng/L and 7200 ng/L, respectively (Yamazaki et al., 2015). In addition, in samples of surface water collected during the summer of 2002 in The Netherlands, BPA was reported at up to 21 µg/L, although at that time the regulation of bisphenols was not as stringent (Belfroid et al., 2002).
In sediments from industrial areas in the USA and Japan, BPA was reported as a few ng/g, while for those in Korea, the mean BPA was 567 ng/g (maximum, 13,370 ng/g). The mean BPF and BPS in Korea were 69.7 and 12.37 ng/g, respectively. Other bisphenols were detected at concentrations of 2 ng/g or less (Liao et al., 2012b). Similarly, Lan et al. (2019) detected BPA in sediment samples in China at 521 ng/g. However, again in China, bisphenol AF (BPAF) was reported to be predominant in sediment samples with a maximum concentration of 2009.8 ng/g, which can be attributed to its use in the production of phenolic resins and fluoroelastomers (Yang et al., 2014b). BPA and other bisphenols have also been reported to contaminate indoor dust. The most commonly detected bisphenols were BPA, BPS and BPF, at mean concentrations from 0.096 to 1.6 µg/g. However, in certain cases, BPA reached 32 µg/g and BPF reached 110 µg/g, as it is an important substitute for BPA (Liao et al., 2012a; W. Wang et al., 2015). As thermal paper is recycled, these substances can find their way back into everyday life, as has been shown for BPA. Therefore, they can occur in other paper products, such as magazines, leaflets, newspapers, paper towels and toilet paper, with a concentration of 14.4 µg/g reported (Liao & Kannan, 2011).
Bisphenol A and its analogues were also found in 75% of food samples in one study, with a mean concentration of 4.38 ng/g fresh weight (Liao & Kannan, 2011). BPA was found predominantly in liver and muscle tissue of fish, where it ranged from 1 to 105 ng/g, generally as higher in liver than muscle tissue. Overall, the highest BPA concentrations have been reported for Greenland shark (105 ng/g), which is at the top of the food chain (Ademollo et al., 2018; Barboza et al., 2020; Belfroid et al., 2002; Errico et al., 2017; Ros et al., 2016). Furthermore, bisphenol-F-diglycidyl ether has been reported for canned sardines (0.1-3.8 µg/g), tuna (0.1-4.2 µg/g), anchovies (up to 4.1 mg/kg), mackerel (up to 1.6 µg/g), mussels (up to 0.5 µg/g) and oysters (up to 0.2 µg/g) (Theobald et al., 2000). To provide another perspective on these concentrations, if a person eats half of a can of sardines (i.e., 100 g), they will be exposed to up to 380 µg bisphenol-F-diglycidyl ether, or if they consume 150 g fish, they can be exposed to up to 12.7 µg BPA.
Overall, the bisphenols are ubiquitous, with the highest concentrations found in wastewaters, and lower concentrations in rivers and seas, as expected, albeit with some notable exceptions. On the other hand, unexpectedly high concentrations have been reported for indoor dust. The various bisphenols in fish and canned food (as mainly BPA) is another matter for concern, as this represents direct exposure of humans to bisphenols.
3.4. Fate in the environment
Bisphenols have different stabilities under different conditions. The clogP values of BPA, bisphenol B (BPB), BPE, BPF and BPS are 3.06, 3.40 3.02, 2.58 and 1.88, respectively. D. Chen et al. (2016) ranked the degradation of bisphenol analogues under anaerobic conditions in an aquatic environment, where BPF was the most biodegradable, followed by BPS and BPA, then BPE, and the least biodegradable was BPB (i.e., BPF > BPS, BPA > BPE > BPB). In an aquatic environment, BPF degrades faster than BPA, while BPS, BPB and bisphenol P (BPP) tend to be more resistant to biodegradation than BPA. When comparing various conditions, bisphenol analogues are less biodegradable in sediments (half-life [t½], 135-1621 days) than in soil (t½, 30-360 days) and water (t½, 15-180 days) (D. Chen et al., 2016).
3.5. Human exposure levels
The major routes of exposure to BPA are ingestion, inhalation or dermal ingestion. Exposure can occur via food packaging, as BPA can leach from food and beverage containers, dust, dental materials, medical devices, thermal paper and toys and articles for children and infants. The daily intake of BPA is higher than that of the other bisphenols. Based on the urinary excretion data, the estimated daily intakes of BPA, BPF, BPS, BPP, bisphenol AP, BPB, bisphenol Z (BPZ), and BPAF have been reported as 2.53, 0.68, 0.60, 0.41, 0.36, 0.29, 0.24 and 0.06 μg/day, respectively (Wang et al., 2020). Most of the ingested BPA is absorbed orally (up to 77%) (Gayrard et al., 2019), while only 1.7% to 3.6% is absorbed through the skin (Toner et al., 2018). Similarly, BPS is almost 100% absorbed in the gastrointestinal tract. Both BPA and BPS undergo glucuronidation either in the intestine (BPA: 44%) or the liver (BPA: 53%), whereby BPS is glucuronidated (41%) (Gayrard et al., 2019) or sulphated; subsequently they are excreted via the kidneys (Fenichel et al., 2013).
Bisphenols have been detected in blood, adipose tissue, placenta, breast milk and urine samples (see Table 4). In blood samples of pregnant women, BPA has been reported to range from 0.4 to 86 µg/L, with the sum of bisphenols at 144 µg/L (Cambien et al., 2020; González et al., 2019; Jin et al., 2018; Li et al., 2020°). In urine samples from children, women and men, bisphenols can range from 0.32 to 1.84 μg/L (Radwan et al., 2018; Snoj Tratnik et al., 2019; Venisse et al., 2014; Yang et al., 2014a). Interestingly, a higher mean bisphenol concentration was reported for children (1.81 μg/L) compared to their mothers (1.02 μg/L) and fathers (0.32 μg/L) (Snoj Tratnik et al., 2019). BPA has been detected in adipose tissue of humans at a mean concentration of 5.83 ng/g (Fernandez et al., 2007). It is worth noting that BPA has also been detected in placental tissue, at up to 22.2 ng/g (BPA) (Jiménez-Díaz et al., 2010). Of particular concern, the colostrum from women in France has also been reported to contain BPA (1.87 μg/L), thus even infants are exposed to bisphenols (Migeot et al., 2013).
Table 4
Occurrence of bisphenols in human tissues.
Tissue
|
Bisphenol
|
Concentration
|
Reference
|
Blood from workers at hazardous waste incinerator
|
BPA
|
0.46 µg/L
|
(González et al., 2019)
|
Plasma
|
BPA
|
0.4 µg/L
|
(Jin et al., 2018)
|
BPS
|
0.15 µg/L
|
BPAF
|
0.073 µg/L
|
Serum of pregnant women
|
Sum of BPs
|
up to 144 µg/L
|
(A. Li et al., 2020a)
|
BPS
|
0.113 µg/L
|
Blood
|
BPA
|
0.266 – 86.831 µg/L
|
(Cambien et al., 2020)
|
Adipose tissue
|
BPA
|
5.83 ng/g
|
(Fernandez et al., 2007)
|
Placenta
|
BPA
|
5.7-22.2 ng/g
|
(Jiménez-Díaz et al., 2010)
|
Colostrum
|
BPA
|
1.87 µg/L
|
(Migeot et al., 2013)
|
Urine
|
BPA, BPS, BPF, BPAF
|
up to 4.38 µg/L
|
(Yang et al., 2014a)
|
BPA
|
children: up to 1.81 µg/L
|
(Snoj Tratnik et al., 2019)
|
mothers: up to 1.02 µg/L
|
fathers: up to 0.32 µg/L
|
BPA
|
up to 1.84 µg/L
|
(M. Radwan et al., 2018)
|
BPA
|
up to 1.378 µg/L
|
(Venisse et al., 2014)
|
n.d. not detected