Review of Environmental Fate and Effects of Selected
Phthalate Esters

7 Butylbenzyl Phthalate (BBP)

7.1 Physico-chemical properties
7.1.1 Water solubility
7.1.2 Octanol-water partition coefficient
7.1.3 Summary
7.2 Environmental concentrations and fate
7.2.1 Concentrations in the environment
7.2.2 Abiotic degradation
7.2.3 Biodegradation
7.2.4 Bioaccumulation
7.2.5 Summary and conclusion
7.3 Effects
7.3.1 Toxicity to micro-organisms
7.3.2 Toxicity to algae
7.3.3 Toxicity to invertebrates
7.3.4 Toxicity to fish
7.3.5 Estrogenic effects
7.3.6 Summary and conclusions
7.4 Environmental hazard classification
7.5 PNEC for the aquatic compartment
 

BBP is used to plasticize or flexibilize synthetic resins, mainly polyvinylchloride /6/.

7.1 Physico-chemical properties

BBP (C19H20O4), CAS No.: 85-68-7, with a alkyl chain length of 4,7 (aryl) /1/ is a colourless oily liquid. The molecular weight is 312.4 g/mol. BBP has a melting point of about -35°C and a boiling point at 195-205°C /6/. The density is 1.111 g/ml at 25°C and the vapour pressure is 5.0·10^-6 mmHg at 25°C /1/.

7.1.1 Water solubility

For BBP, several aqueous solubility data are referred to in the literature ranging from 0.70 to 40.2 mg/l. The water solubility has been calculated to 0.67 mg/l /7/. In a literature review by Staples et al. /1/, it was concluded that a water solubility of about 2.7 mg/l was the most likely value based on available evidence.

7.1.2 Octanol-water partition coefficient

As for solubility, there are several different values in the literature for the octanol-water partition coefficient K_ow, differing with a factor of 22. Reported log K_ow values for BBP range from 3.57 to 4.91. A log K_ow of 4.91 has been calculated /7/. According to Staples et al. /1/, a log K_ow of 4.59 is the most likely value based on available evidence.

7.1.3 Summary

The approximate physico-chemical properties on BBP are summarized in Table 7.1.

Table 7.1
Physico-chemical properties of Butylbenzyl Phthalate (BBP)

7.2 Environmental concentrations and fate

7.2.1 Concentrations in the environment

The content of BBP in waste water and sewage sludge from Danish treatment plants has been measured at several occasions during recent years. An overview of the results is given in Table 7.2.

Table 7.2
link to table

It is a general picture that a high removal of BBP from the wastewater is found during the wastewater treatment. Mass balances have shown that only about 0.3% of the amount in the inlet water is found in sludge /9/, which indicates that a considerable amount of BBP may be reduced by anaerobic degradation.

A large number of data on concentrations of BBP in the environment is given in /3/ and only a brief overview will be given here.

Concentrations of BBP in 31 American rivers, lakes and estuaries are in the ranges from 0.2 to 2.4 µg/l, 0.35 to 0.45 µg/l and 0.3 µg/l, respectively. In surface water in German rivers and their main effluents, BBP was detected in concentrations of up to 3.4 µg/l and 49 µg/l, respectively.

Concentrations of BBP have been detected in river and lake sediments in the ranges from 60 to 14,000 µg/kg and 400 to 420 µg/kg, respectively. No information was found concerning BBP levels in marine sediments.

Soil sampled in the neighbourhood of phthalate-emitting plants contained concentrations of BBP of up to 100 µg/kg dry matter.

BBP has been detected in concentrations from 2.25 to 9.0 ng m^-3 in the city of Barcelona, Spain.

In biota, BBP has been detected at concentrations of up to 39 µg/kg wet weight (fish) and of up to 1.3 µg/kg dry matter (terrestrial plants).

7.2.2 Abiotic degradation

Wolfe et al. (1980) /2/ measured the hydrolysis rate constant of BBP and estimated a half-life of >0.3 years at alkaline conditions. The hydrolysis half-life at neutral pH and 25°C range is estimated to 1.4 years /7/.

No experimental data on photodegradation of BBP in the atmosphere are available. Estimated photodegradation half-lives are in the range from 0.5 to 5 days /4, 7/. Photodegradation of BBP in a 1 mg/l aqueous solution was studied by Gledhill et al. (1980) /104/ who reported less than 5% degradation in 28 days. Thus, in the aquatic environment only insignificant photodegradation is expected /1, 3/.

7.2.3 Biodegradation

The ready biodegradability of BBP was determined in the OECD 301C test resulting in a degradation of 81% after 14 days of incubation /12/. Staples et al. (1996) /1/ have reviewed the biodegradability of BBP and refer to three studies showing an ultimate biodegradability in the range from 10% to 65% after 28-30 days of incubation.

Saeger & Tucker (1976) /105/ tested the ultimate biodegradability during 27 days by incubating BBP with sludge, which had been acclimated for 14 days. 96% biodegradation was determined. Sugatt et al. (1984) /14/ using an acclimated inoculum demonstrated a biodegradability of BBP of 43% after 28 days of exposure. Györkös (1996) /3/ refers to an investigation by Gledhill et al. (1980) /104/ showing 96% biodegradation after 28 days by using an acclimated inoculum. Staples et al. (1996) /1/ report that the mineralization of BBP ranged from 66% to 96% after 27-28 days by use of acclimated inocula.

Saeger & Tucker (1976) /105/ determined the primary biodegradation of BBP in river water samples and found a rapid degradation of about 80% after 2 days of incubation.

In a semi-continuous activated sludge (SCAS) test, Saeger & Tucker (1976) /105/ determined a primary degradation of 93-99% of BBP after 24 hours of incubation.

Howard (1989) /11/ refers to an investigation demonstrating more than 90% degradation of BBP in about a week. Györkös (1996) /3/ refers to investigations showing 63% degradation after 1 week and more than 90% after 40 days under anaerobic conditions /67/, 50% after 29 days of incubation /106/, and 97% during anaerobic digestion /107/. Furthermore, Györkös (1996) /3/ refers to 78% and 88% degradation of BBP in anaerobic salt-marsh and fresh-water sediments after 22 and 35 days, respectively, of incubation in a study by Painter & Jones (1990) /106/. Staples et al. (1996) /1/ refer to studies showing anaerobic primary biodegradation at 30-37°C in the range from 50% to 100% for 7-100 days and anaerobic ultimate biodegradation in the range from 0% to 100% for 28-70 days.

Howard (1989) /11/ refers to an investigation demonstrating more than 95% primary degradation of BBP in a lake water microcosm after 7 days and 51-65% mineralization after 28 days. Györkös (1996) /3/ refers to investigations showing 80% primary degradation in unacclimated river water /105/ and 100% primary degradation in river water within 9 days /104/.

7.2.4 Bioaccumulation

In the following, only bioaccumulation studies on fish will be referred to as no studies on algae, crustaceans and insects were found.

Several bioaccumulation studies have been performed on Bluegill sunfish (Lepomis macrochirus) with total BCFs varying from 188 (17 days of exposure with a flow through test procedure and an exposure concentration of 2 µg/l) /126/ to 663 (flow through test procedure and an exposure concentration of 9.7 µg/l; exposure period is not known) /17/. The total BCF was by Carr et al. (1992) /64/ determined to 449 (3 days of exposure with a flow through test procedure and an exposure concentration of 34 µg/l), the corresponding BCF of the parent compound was by Staple et al. (1996) /1/ calculated to 12.

7.2.5 Summary and conclusion

BBP seems to be efficiently removed from waste waters based on the low output concentrations compared to inlet concentrations in sewage treatment plants. However, large differences exist between different treatment plants. Degradation may account for some of the reduction seen but accumulation in sludge may be important based on the high concentrations of BBP measured in some sludge samples.

BBP has been detected in soil and water (rivers, lakes and estuaries) at variable concentrations. In the aquatic environment, BBP concentrations of up to 49 µg/l have been found. In sediments BBP has been detected in concentrations of up to 14,000 µg/kg and in biota BBP has been detected at concentrations of up to 39 µg/kg wet weight (fish) and up to 1,256 µg/kg dry matter (terrestrial plants).

Hydrolysis and photodegradation are not significant degradation routes of BBP in the aquatic environment.

BBP is readily biodegradable in standard laboratory tests and, hence, the substance is expected to be mineralized rapidly in the aerobic part of a sewage treatment plant. The studies of anaerobic biodegradability indicate a potential for mineralization of BBP during anaerobic treatment of sludge.

BBP is bioaccumulative in aquatic biota, which is demonstrated by the experimentally derived BCF value of up to 663 for fish.

7.3 Effects

7.3.1 Toxicity to micro-organisms

The toxicity studies with micro-organisms are summarized in Table 7.3. The table contains data on both bacteria and protozoa.

Table 7.3
link to table

7.3.2 Toxicity to algae

The toxicity studies with BBP for freshwater and marine algae are summarized in Table 7.4.

Table 7.4
link to table

The toxicity data obtained on the different algae species seem to be in close agreement.

7.3.3 Toxicity to invertebrates

The short-term toxicity data on BBP to freshwater and marine invertebrates are presented in Table 7.5. and the long-term toxicity data on BBP to freshwater and marine invertebrates are presented in Table 7.6.

Table 7.5
link to table

Table 7.6
link to table

In all tests performed, except one acute test with Mysidopsis bahia, the effect concentrations of BBP were at concentrations equal to or below the water solubility of the substance, furthermore, many of the effect concentrations determined are based on measured exposure concentrations.

7.3.4 Toxicity to fish

The short-term toxicity data on BBP to freshwater and marine fish are presented in Table 7.7. and the long-term toxicity data on BBP to fresh-water and marine fish are presented in Table 7.8.

Table 7.7
link to table

Table 7.8
link to table

In all tests performed, except for one acute test with Lepomis macrochirus, the effect concentrations of BBP were at concentrations equal to or below the water solubility of the substance. Furthermore, most of the effect concentrations determined are based on measured exposure concentrations. From the results obtained by Ozretich et al. (1983) /115/ with Cymatogaster aggregata, it can be seen that no further toxicity is obtained when the exposure period is increased from 96 h to 165 h. This indicates that steady state conditions and thus the maximum toxicity of BBP are reached during the 96 h test period.

7.3.5 Estrogenic effects

Jobling et al. (1995) /100/ studied the estrogenic effects of a range of chemicals, including BBP, commonly found in sewage effluents. Using cytosolic extract from liver of rainbow trout, Oncorhynchus mykiss, in which estradiol receptor-binding sites are present in both female and male fish, Jobling et al. (1995) /100/ documented that BBP binds to the receptor, inhibiting the binding of natural estradiol. It has also been shown that BBP has mitogenic effect on the in vitro growth of human breast cancer cell (ZR-75) at test concentrations of 3.12 mg/l. In transiently transfected MCF 7 breast cancer cells, BBP was reported to affect the transcriptional activity of the estrogen receptor. BBP concentrations in the range from 0.31 to 31.2 mg/l stimulated the activity.

In a study by Sharpe et al. (1995) /102/, BBP was found to have estrogenic activity using a recombinant yeast screen. The relative potency of BBP was approx. 1&middot10⁶ times less than 17b-estradiol. In addition, it was found that BBP at a concentration of 10^-11 M increases the transcriptional activity in the presence of natural 17b-estradiol.

Sharpe et al. (1995) /102/ assessed whether exposure of male rats to xenoestrogens during gestation and during the first three weeks after birth affects the size of their testes and sperm production in adult life. BBP was added to the drinking water of the pregnant female rats at low concentrations (1 mg/l). In adult life, males exposed in this way had testes that were reduced in size by 5-13% and a 10-21% reduction in their sperm production capacity. These effects were manifest in animals showing no gross changes. Meek et al. (1997) /103/ measured changes in reproductive organs of female rats. They showed that BBP produces no estrogenic activity. However, it has to be noted that the conclusions made by Meek et al. (1997) /103/ are built on unpublished data.

7.3.6 Summary and conclusions

Variable results were found in the toxicity tests with micro-organisms.

BBP has been shown acutely toxic (EC₅₀ or LC₅₀ values) to algae, crustaceans and fish in the range from 0.1 to 2.1 mg/l, in which algae seem slightly more sensitive than crustaceans and fish. BBP is thus considered very toxic to aquatic organisms.

NOEC levels in chronic toxicity tests with algae, crustaceans and fish were observed in the range from 0.03 to 0.35 mg/l.

BBP has shown to be estrogenic in vitro, stimulating human breast cancer cell growth and transcriptional activity of the estrogen receptor. BBP has been shown to significantly reduce testis size and sperm producing capacity of male rats exposed to low concentrations of the chemical during gestational and the lactational period. BBP has shown to be testis toxic in adult rats, causing atrophy of the testes, prostate, seminal vesicles and epididymis.

Lack of in vivo estrogenic effects studies in wildlife makes assessment of the potential estrogenic effects of BBP in wildlife difficult. However, data on male rats exposed to low concentrations of BBP during gestation and the lactation period indicate that estrogenic substances may affect the reproductive ability of adult male rats.

7.4 Environmental hazard classification

BBP has been shown acutely toxic (EC₅₀ or LC₅₀ values) to algae, crustaceans and fish in the range from 0.1 to 2.1 mg/l, in which algae seem slightly more sensitive than crustaceans and fish.

NOEC levels in chronic toxicity tests with algae, crustaceans and fish were observed in the range from 0.03 to 0.35 mg/l.

BBP is readily biodegradable in standard laboratory tests.

BBP is bioaccumulative in aquatic biota, which is demonstrated by the experimentally derived BCF value of up to 663 for fish.

The water solubility of BBP is » 2.7 mg/l which is above the cut-off value of 1 mg/l.

Considering the criteria for environmental hazard classification (EEC 1993) and the above evaluation of the environmental fate and effect of Butylbenzyl phthalate, it is proposed that BBP is classified "N; R50/53: Very toxic to aquatic organisms, may cause long-term adverse effects in the aquatic environment".

7.5 PNEC for the aquatic compartment

Toxicity data are available on short-term tests with bacteria, protozoa, algae, crustaceans and fish. All toxicity data are more or less in the same range with EC/LC₅₀ values from 0.1 mg/l to a few mg/l. Long-term toxicity data are available on algae, crustaceans and fish with NOEC values in the range from 0.03 to 0.35 mg/l. An assessment factor of 10 for the lowest long-term NOEC should be used for deriving a PNEC_aquatic. However, considering the fact that the substance is bioaccumulative and has a potential estrogenic activity, an extra safety factor of 10 is used resulting in a proposed PNEC_aquatic = 0.0001 mg/l.