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Diisononyl phthalate (DINP) FactSheet

CAS Nos: 68515-48-0 and 28553-12-0

Diisononyl phthalate (DINP) is a member of the group of esters commonly known as phthalates1.  DINP belongs to the High Molecular Weight (HMW) group with straight carbon side chain of ≥ C7 or ring structure.

There are no reports of DINP being manufactured as a raw material in Australia. DINP is imported into Australia as a raw material for local formulation or as a mixture in ready-to-use products.

In 2002, the total volume of DINP imported for industrial uses was between 1000 and 10 000 tonnes, but by 2004 that had dropped to around 600 tonnes annually. Current market consumption volume of DINP in Australia is between 1600 to 2000 tonnes per annum.

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

DINP is NOT listed in the Safe Work Australia List of Designated Hazardous Substances contained in the Hazardous Substances Information System3 (HSIS) the Standard for Uniform Scheduling of Medicines and Poisons4 (SUSMP), or the National Transport Commission's Australian Dangerous Goods Code5.

How DINP is used

DINP is used in a diverse range of industrial products such as electrical wire and cables, flexible PVC sheeting, coated fabrics, automotive parts, building and construction (waterproofing), vinyl flooring, footwear, sealings, lamination film and in PVC-containing school supplies (such as scented erasers and pencil case).

DINP can be blended into a paste (plastisol), for coating (tarpaulins, synthetic leather and wall covering) and rotomoulding (toys, play and exercise balls, hoppers) applications. DINP is used in non-polymer applications such as adhesives, paints, surfactants and printing inks for T-shirts. It can be found in plasticine, in several categories of toys (plastic books, balls, dolls and cartoon characters) and in baby products (changing mats/cushions) which could be placed in the mouth. DINP has been found in other articles that may come into contact with children (clothes, mittens, coverage of pacifiers, PVC-containing soap packaging and shower mats).

In Australia DINP is used mainly as a plasticiser (plastic softener) for polyvinyl chloride (PVC) products and in other polymers for adhesives, vinyl flooring, laminators, resins, surfactants, screen printing inks and flexible PVC products (gaskets and gumboots), with a small proportion used in children's toys. In imported PVC toys, DINP may be present at a concentration range estimated to be between 0.005% and 35%.

Information on the use of DINP provided by Australian industry does not indicate that it is used in cosmetic and personal care products and there was no available information to indicate that DINP is used in cosmetics overseas. In addition, there is no available information to support the possibility that high molecular weight phthalates such as DINP might be used as a substitute for low- and mid-molecular weight phthalates commonly used in cosmetics.

Background

The purpose and scope of the DINP assessment by the National Industrial Chemicals Notification and Assessment Scheme (NICNAS) was to determine the public health risks from the use of DINP in consumer products such as toys, child care articles and cosmetics, particularly after repeated or prolonged exposure.

The decision to declare DINP for assessment was based on:

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

Health effects

Data from animal and human studies indicate that DINP is rapidly absorbed following oral administration. The oral bioavailability of DINP is considered to be 100% for both adults and children. Bioavailability via dermal (skin) absorption is expected to be not greater than 4% in humans. Tissue distribution of DINP is widespread but there is no evidence of accumulation. DINP is rapidly metabolised to monoisononyl phthalate (MINP), which is further metabolised to form additional metabolites or hydrolysed to phthalic acid and excreted predominantly in urine.

DINP has low acute toxicity via all routes. DINP is a slight skin and eye irritant, and shows minimal sensitisation potential. DINP is not genotoxic or carcinogenic.

The main target organs in several animal species following repeated oral exposure to DINP are the liver and kidney. Following dermal repeated exposures, slight to moderate erythema and desquamation were observed in rabbits.

Although available human data are limited and do not provide sufficient evidence for a causal relationship between exposure to DINP and possible adverse health effects, elements of plausible mode of action for the effects of DINP on the male reproductive system (reduced testicular testosterone), offspring growth (decreased pup weight) and sexual differentiation (decreased anogenital distance and increased nipple retention) are considered relevant to humans, where the exposure level of DINP is high and within a critical window of development.

Public exposure and health risk

NICNAS used a margin of exposure (MOE) approach in its assessment of public health risks from DINP exposure. (A margin of exposure (MOE) methodology is used in international assessments to characterise risks to human health associated with exposure to chemicals. The MOE provides a measure of the likelihood that a particular adverse health effect will occur under the conditions of exposure. As the MOE increases, the risk of potential adverse effects decreases.)

There is no evidence of DINP being used in cosmetics in Australia or overseas, therefore the assessment was conducted to address the declaration in respect of concerns regarding the use of toys and child care articles by children.

Use of toys and child care articles by children

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

NICNAS used overseas studies to determine migration rates for DINP 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 maximum mouthing time of 2.2 hours per day, with a typical exposure scenario based on an average daily mouthing time of 0.8 hours per day.

DINP 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. NICNAS estimated health risks for children for both systemic (liver and kidney) toxicity and fertility/developmental-related effects – all of which are potentially associated with repeated handling and mouthing of toys containing DINP. Overall, the risk estimates indicate low concern for children at the current reported levels of DINP in toys and child care articles.

The cumulative exposure to phthalates can arise from the presence of several phthalates in toys and child care articles or from exposure to a range of products containing this group of chemicals. Risks from cumulative exposure of children to DINP in toys and child care articles with or without DEHP at 1% (maximum allowable concentration under the Australian consumer protection law), together with co-exposure to another phthalate, DEP in cosmetics at 0.5% in body lotions (maximum allowable concentration under states and territories poisons legislation) are considered low, because cumulative MOEs for the three critical health effects identified are all above 100. An MOE of greater than 100 in risk characterisation is usually regarded as an indication of low concern as it encompasses the conservative default uncertainty factors of 10 each for intraspecies and interspecies variability.

Recommendations

Current risk estimates do not indicate a health concern from exposure of children to DINP in toys and child care articles even at the highest (reasonable worst-case) exposure scenario considered.

The risks from cumulative exposure of children to DINP in toys and child care articles with or without DEHP (at maximum 1%) together with co-exposure to DEP (at maximum 0.5%) in body lotions were found to be acceptable, based on current public health risk management measures.

No recommendations to public health risk management for the use of DINP in toys and child care articles are required based on the findings of this assessment. However, secondary notification requirements have been specified as indicated below.

Secondary notification

Under Section 64 of the Act, 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 DINP;
  • DINP being used in cosmetic products;
  • additional sources of public exposure to DINP other than toys and child care articles and cosmetics being identified, 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.

More information

  1. Hazard assessments on 25 phthalates, available on the NICNAS website: www.nicnas.gov.au.
  2. Phthalates Hazard Compendium—comparative information on the use and hazards associated with 24 ortho-phthalates also available under www.nicnas.gov.au
  3. Hazardous Substances Information System (http://hsis.safeworkaustralia.gov.au/)
  4. Standard for Uniform Scheduling of Medicines and Poisons, available under www.tga.gov.au
  5. The National Transport Commission's Australian Dangerous Goods Code (available under www.ntc.gov.au)
  6. National Industrial Chemicals Notification and Assessment Scheme (NICNAS) – contact NICNAS staff for assistance – see below.
  7. Legislation mentioned in this information sheet can be found on the Australasian Legal Information Institute web site at www.austlii.edu.au.

NICNAS contact details

More information about NICNAS and on the use of industrial chemicals can be found on the NICNAS website at www.nicnas.gov.au.  Or you can contact NICNAS via:
Free call: 1800 638 528   E-mail: info@nicnas.gov.au

Updated May 2013

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