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Dibutyl phthalate (DBP)

CAS No: 84-74-2

Dibutyl phthalate (DBP) is a member of the group of chemicals commonly known as phthalates, used worldwide as solvents (to dissolve other substances) and plasticisers (to make other substances softer or more pliable).

In preparing its assessment of DBP, the National Industrial Chemicals Notification and Assessment Scheme (NICNAS) found no reports of the phthalate being manufactured as a raw material in Australia; DBP is imported into Australia mainly as a component of finished products or mixtures and also as a raw material for local formulation and processing.

The yearly introduction volume of DBP is relatively low and it was not included on the high volume industrial chemicals (HVIC) list for 2002 or 2006, as the quantity introduced in those years was below the annual reporting threshold of 1000 tonnes per year. More than 350 tonnes was introduced to Australia in 2004. In 2005, the volume of raw material introduced—with the potential to be used in applications such as toys and cosmetics—was reported as approximately 95 tonnes; in 2006 it was 80 tonnes.

DBP is listed in the Safe Work Australia List of Designated Hazardous Substances contained in the Hazardous Substances Information System (HSIS) as a Reproductive Toxicant Category 2 (requiring it to be labelled with the risk phrase [R61]—May cause harm to the unborn child); and Reproductive Toxicant Category 3 (requiring the risk phrase [R62]—Possible risk of impaired fertility).

DBP is NOT listed in the Poisons Standard (Standard for Uniform Scheduling of Medicines and Poisons—SUSMP).

There are currently no restrictions on the manufacture, import or use of DBP in Australia.

How DBP is used

DBP is used in a diverse range of industrial applications including as a plasticiser in resins and polymers. DBP is also used as a softener in adhesives, lacquers, varnishes and printing inks. DBP is used in cosmetics as a perfume solvent and fixative; a suspension agent for solids in aerosols; a lubricant for aerosol valves; an anti-foamer; a skin emollient and plasticiser in nail polish and fingernail elongators (extensions).

In Australia DBP is mainly used in industrial applications such as surface coatings (paints, pigments, floor coatings); car mat backing; polymer emulsions for adhesives; in polyvinyl chloride (PVC) compounds such as wire cable tubing and footwear; in nitrocellulose lacquers for automotive refinishes, epoxy sealants, leather paint, galvanised iron primers and texture finishes, floor polish and sealers, textile wet processing (processing of textiles, using water) products, ectoparisiticides (drugs that kill parasites that live on the body) for horses and in screen printing inks. It is also imported for use as a laboratory research and development chemical in academic institutes and quality control laboratories.

Consumer uses in Australia include sealants, fragrance bases for household, personal care and cosmetic products with the highest concentration reported as 7% for nail polish.

DBP is also present in exercise balls, hoses, rubber sheets and in children's toys—including those intended for children aged 0-6 years. The typical concentration of DBP in an unspecified set of products for children was identified as 0.5%. The low content indicated for DBP in children's toys and childcare articles coincides with its physico-chemical characteristics (i.e. high volatility) that makes DBP inappropriate for use as the primary plasticiser for PVC.

However, it may be used as a secondary plasticiser together with other phthalates such as diisononyl phthalate (DINP) and diethylhexyl phthalate (DEHP) that are being widely reported to be used in PVC at high concentrations.

Background to NICNAS assessment

NICNAS assessed DBP to determine the health risks to adults and children from its use in consumer products such as cosmetics, toys and childcare articles—particularly after repeated or prolonged exposure.

NICNAS based its decision to declare DBP for assessment on:

  • ubiquitous use of phthalates including DBP as plasticisers in industrial and consumer products;
  • consumer products being potentially significant sources of repeated and long-term exposure of the public to DBP through migration and leaching from the products;
  • concerns regarding potential adverse health effects, particularly reproductive and developmental effects, from DBP exposure; and
  • current overseas restrictions on the use of phthalates including DBP in certain consumer products.

Restrictions (either interim or permanent) on the use of DBP in toys and childcare articles have been implemented—as a precautionary measure—in the European Union (EU), United States of America (US) and Canada. There are currently no restrictions on the use of DBP in toys and childcare articles in Australia, Asia and other non-EU countries.

EU legislation also prohibits the use of DBP in cosmetics. In the US (except the state of California) and Canada, the use of DBP in cosmetics and personal care products is not restricted.

Health effects

DBP is rapidly absorbed and excreted after being ingested (swallowed). After ingestion, it is 100% absorbed (becoming bioavailable) in humans, Bioavailability through skin absorption is at a lower rate (5%). Data are limited on the absorption of DBP by breathing; a default of 100% is therefore applied for the purposes of characterising (determining) risk.

DBP has low acute toxicity through all routes of exposure, and low eye, skin and respiratory irritation and skin sensitising potential.

DBP has been reported to be non-genotoxic (i.e. does not cause genetic mutations) in most in vitro and all in vivo animal tests performed to standard testing guidelines. No adequate long-term carcinogenicity (cancer-causing) studies with DBP in laboratory animals are available. However, based on the information available for genotoxicity, DBP is not likely to be a genotoxic carcinogen.

Target organs affected by toxic effects related to repeated DBP exposure in rodents include:

  • the liver—where weight changes, degeneration of cells, activation of fatty acid metabolising enzymes, alterations in fatty acids associated with increasingly rapid production of peroxisomes (enzyme-producing microbodies inside cells) were observed; and
  • the reproductive system, particularly in males—where decreased weight of testes and accessory organs, spermatocyte depletion, sperm producing channels (seminiferous tubule) degeneration, and disturbances in serum and testicular testosterone were observed.

Repeat-dose toxicity studies on multiple generations of rodents showed testicular toxicity. Both fertility and development are affected in the parents and following generations. The toxicity in male rodents involves overt effects on the reproductive tract organs. DBP also affects testosterone synthesis in male rodents. This is particularly demonstrated in multigenerational and developmental studies where male rodents have undergone gestational (in the uterus prior to birth) exposure to DBP.

While human studies are limited, the adverse effects on the development and function of the reproductive system in experimental animals are considered relevant to humans, where exposure to DBP occurs during the critical stages of development.

Measuring public exposure and health risk

NICNAS assessed public health risks from DBP exposure in consumer applications by using a margin of exposure (MOE) approach—commonly used in international assessments to characterise risks to human health associated with exposure to chemicals.

MOE measures the likelihood that a particular adverse health effect will occur under the conditions of exposure, and is derived by comparing the DBP dose at which there is no observed adverse effect on target organs and/or systems in laboratory animals (the 'no observed adverse effect level'—NOAEL) with the estimated human dose (EHD) of DBP. The greater the MOE, the lower the risk of potential adverse effects—so in risk characterisation, an MOE above 100 indicates low concern.

Public health risks from DBP exposure were assessed using an MOE for two scenarios:

  • children using toys and childcare articles; and
  • the general population using cosmetic products.

MOE assessments which compared the DBP dose at which no adverse reproductive effects were observed in experiments, with estimated internal DBP doses for children using toys containing 0.5% DBP, derived an MOE of above 100 for the 'typical' and 'worst case' scenarios of toy use.

However, estimation of MOEs comparing the DBP dose at which no adverse reproductive effects were observed in experiments, with estimated internal DBP doses in individuals using cosmetics containing 0.25% DBP, derived an MOE for the worst case scenario of less than 100.

1.   Children using toys and childcare articles

For the toy and child care articles exposure scenario, two exposure routes for children were considered: dermal (skin) exposure during normal handling of toys and child care articles containing DBP, and oral exposure during mouthing, sucking and chewing of these products.

NICNAS used overseas studies to determine migration (transfer of a chemical from a product) rates for DBP from chewing. These studies indicated that children's mouthing behaviour, and therefore the potential for oral exposure, is greatest between six and 12 months of age, and a reasonable 'worst-case' exposure scenario considered a maximal mouthing time of 2.2 hours per day, with a 'typical' exposure scenario based on an average daily mouthing time of 48 minutes per day.

DBP has low acute toxicity, low skin and eye irritation and skin sensitising potential, so the risk of adverse acute effects for children arising from handling toys is low. The critical health effects observed in animals—and applicable to humans—were those to the development and function of the reproductive system.

NICNAS estimates of the health risks for children for reproductive/developmental effects under both the 'worst' and 'typical' exposure scenarios of repeated handling and mouthing of toys containing DBP, indicate low concern for children at the current reported low levels of DBP in these applications.

The risk was also considered from cumulative exposures to DBP and other phthalates used in toys and childcare articles, and from combined exposure to phthalates from multiple sources, i.e. use of toys and personal care products. In all cases, the MOE for the critical health effects for children from cumulative exposure to DBP used as a secondary plasticiser at 0.5% in toys and childcare articles—together with DINP and DEHP at maximum 41.5% and 1%, respectively—was found to be above 100, indicating a low risk. Similarly, the MOE for critical health effects from combined exposure to DBP in toys and childcare articles—together with exposure to diethyl phthalate (DEP) at maximum 0.5% in body lotions—was found to be above 100, indicating a low risk.

Risks from cumulative exposure to DBP and other phthalates will be considered on completion of other phthalate PEC assessments, and if required, further risk mitigation measures may be recommended.

2.   The general population using cosmetic products

The main route of exposure to DBP in the cosmetics and personal care products scenario for the general public is through skin contact, although it is also possible to inhale it from products applied as aerosols. Current information does not indicate the use of DBP in products most prone to accidental oral ingestion (toothpastes, mouthwashes, lipsticks and lip-glosses). NICNAS based its 'worst case' exposure scenario for combined cosmetics use on international use patterns.

Given the low acute toxicity, low irritation and sensitisation potential of DBP, the risk of acute adverse effects for consumers exposed to DBP through cosmetics is low. However, potential risks from DBP use in cosmetics relate to the development and function of the reproductive system.

The MOE for reproductive or developmental effects estimated for the 'worst case' scenario of multiple cosmetic product use containing DBP is below 100. The low MOE indicates concern for the general population and high concern for the sub-populations most at risk for reproductive developmental effects in their progeny—i.e. pregnant and breastfeeding women.

Conclusion

NICNAS's assessment outlines some important new information, provides a higher degree of certainty regarding the low risk from DBP in children's toys and childcare articles, and substantiates concerns about its use in cosmetics.

Current risk estimates do not indicate a health concern for children from DBP in toys and childcare articles—under the exposure scenario considered—where the chemical is used as a secondary plasticiser.

The risks for children from cumulative exposure to DBP in toys and childcare articles—together with the primary plasticisers DINP and DEHP—were found to be low, even considering combined exposure to DEP in body lotions, based on current public health risk management measures. Therefore no recommendations are required for public health risk management of DBP in toys and childcare articles, based on the findings of the NICNAS assessment.

However, the NICNAS assessment found that DBP alone and/or with the simultaneous use of multiple cosmetic products containing DBP by children and the general population can result in high risk of reproductive toxicity.

Therefore, a recommendation to restrict the use of DBP in cosmetics by including it in Appendix C of the Poison Standard (Standard for the Uniform Scheduling of Medicines and Poisons—SUSMP) is warranted.

Appendix C of the Poison Standard lists substances that are prohibited from sale, supply and use because of their known potential harm to human health.

Secondary notification

Under section 64 of the Industrial Chemicals (Notification and Assessment) Act 1989, secondary notification of a chemical that has been assessed may be required if there is a change of any circumstances that may warrant a reassessment. This could include:

  • additional information becoming available on the adverse health effects of DBP;
  • DBP being used in children's toys and childcare articles at a concentration of more than 0.5%;
  • Identification of additional sources of public exposure to DBP other than toys and childcare articles and cosmetics; or
  • additional information or events that change the assumptions for estimating the cumulative risk in this assessment.

The Director of NICNAS must be notified within 28 days of the introducer becoming aware of any of the above. Notifications may be sent to info@nicnas.gov.au.

More information

Last updated: April 2016

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