Benzyl butyl phthalate (BBP) is an organic compound historically used a plasticizer, but which has now been largely phased out due to health concerns.

[2] BBP is classified as toxic by the European Chemical Bureau (ECB) and hence its use in Europe has declined rapidly.

Both the carbonyl C-atoms are weakly electrophilic and therefore targets for attacks by strong nucleophilic compounds.

Besides the carbonyl C-atom target, it contains a C-H bond whereas the H-atom is weakly acidic, which makes it susceptible for deprotonation by a strong base.

Monobutyl phthalate is isolated and then added to a mixture of benzyl bromide in acetone in the presence of potassium carbonate (to keep the pH high to facilitate the substitution reaction required to form the second ester linkage), from which BBP can then be isolated.

[10] In vitro-experiments do show a weak potential of BBP to have an influence on estrogen-mediated gene expression.

Calcium signaling, mediated via P2X, eventually has an influence in cell proliferation and bone remodeling.

During developmental phases of bone remodelling, high environmental exposure of BBP might therefore pose a problem.

One of the authorities, the International Program on Chemical Safety (IPCS), came to the conclusion that exposure to BBP is mainly caused by food intake.

[14] Various studies by authorities, between the 1980s and 2000s, have been done to estimate the general population exposure to BBP in different countries with varying results.

[15] Thus, BBP does not seem to pose a very high risk under conditions of general or occupational exposure based on current estimates.

No primary irritation or sensitization reactions were found in a patch test involving 200 volunteers.

[16] Workers in the PVC processing industry are exposed to higher levels of BBP than the general public and are thus more at risk of experiencing negative health effects.

[17][full citation needed] Long-term occupational exposure to BBP does, however, significantly increase the risk of multiple myeloma.

PVC flooring has been linked to a significant increase in the risk of bronchial obstruction in the first two years of life[14] and in the development of language delay in pre-school aged children.

[19] Moreover, there is evidence suggesting that prenatal exposure to BBP coming from in house dust affects the risk of childhood eczema.

Yet, one study found a link between altered semen quality and exposure to monobutyl phthalate, a major metabolite of BBP.

[22][23][24] The precise teratogenic effects observed in rat fetuses seem to be related to the period of exposure in development.

[24] In a two-generational study male offspring were found to have macroscopic and microscopic changes in the testes, decreased serum testosterone concentrations in addition to reduced sperm production.

Numerous studies have been carried out in animals to elucidate the adverse effects of BBP exposure.

[22] BBP, like other low molecular weight phthalate esters, is toxic to aquatic organisms.

Experiments with mysid shrimp show that BBP is acutely toxic to these organisms.

Following an examination performed in 1997,[28] it was found that biotransformations play a very important role in the degeneration of BBP.

The butyl group gives BBP a slightly more hydrophobic property, compared to other plasticizer it is relatively good soluble.

[29] California's Office of Environmental Health Hazard Assessment (OEHHA), on July 1, 2013, approved a Maximum Allowable Dose Level of 1,200 micrograms per day for BBP.

[30] Canadian Authorities have restricted the usage of phthalates, including BBP, in soft vinyl children's toys and child care articles.