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Evaluation of the health risk to animals playing with phthalate containing toys

2 Animal exposure

• 2.1 The relevant exposure scenario
• 2.2 Occurrence of phthalates in toys
• 2.3 Migration of phthalates from toy
• 2.4 Duration of gastrointestinal passage in dogs
• 2.5 Body weights of dogs
• 2.6 Estimating the exposure
  • 2.6.1 Estimation A - based on measured migration rate
  • 2.6.2 Estimation B - based on 10% (w/w) migration of phthalate

2.1 The relevant exposure scenario

On the Internet, safety information about toys to dogs and cats can be found (e.g. http://www.hunde-info.dk/farlege.shtml). Animal doctors experience that dogs often swallow toys (and many other products as well) and due to the physical properties of the products they can pose a risk to the animals. It is also experienced that those items that were soft plastic when e.g. the dog played with it turns out to be hard and sharp when in the gastrointestinal tract indicating that the softeners present in the product leach out.

Furthermore, information such as “går legetøjet i stykker skal det fjernes fra dyret” is written on some of the analysed toys (Nielsen et al. 2005A).

When the animals bite in the toy, the physical chewing and the presence of saliva result in the extraction of the phthalates. Furthermore, if the toy is swallowed the phthalates can migrate from the piece of toy as long as it is retained in the gastrointestinal tract. Therefore, oral exposure during chewing and biting in the toy as well as the swallowing of parts of the toys is of concern.

The playing behaviour of dogs and cats are somewhat different. In general dogs bite and chew in the toy whereas cats are more likely to play with the toy with the paws. Dermal exposure during the animals playing with the toy is of little concern because the dermal absorption measured on skin is relatively low (Deisinger et al. 1998) and it will be even more reduced because of the fur of the animal.

Therefore, in the present risk assessment the relevant and realistic worst-case exposure scenario will be a dog that bite, chew and swallow a piece of toy that continuously emits phthalates while in the gastrointestinal tract. Dermal exposure will not be considered in the present assessment and it will be assumed that the estimated exposure to dogs will also cover the exposure to cats as it in general is expected to be lower.

The different parameters that will be used in the estimation of oral exposure to dogs chewing and eating the toy will be presented in the following sections.

2.2 Occurrence of phthalates in toys

As mentioned in the introduction the content of DEHP and DINP in 13 PVC containing toys for cats and dogs available on the Danish marked and on the Internet has been analysed. The investigated phthalates were present in all products in concentrations ranging from 6.9 to 54% (v/v) (Table 1).

Exposures will be estimated for minimum, mean and maximum content of DEHP and DINP in the toy.

Table 1. The amount of DINP and DEHP in 13 products of toys for animals

(Nielsen et al. 2005A)

2.3 Migration of phthalates from toy

Several investigations of the migration of phthalates from toys have been performed with both in vivo as well as in vitro extraction methods.

In an investigation by Kùnemann (1998), the release of DINP from PVC samples was measured in 10 test persons both sucking and biting on three different DINP containing (38-43%) specimens (10 cm²). The release ranged from 0.3 - 8.9 μg/10 cm²/min with an average release for each of the three specimens of 1.38, 2.44 and 1.63 μg/10 cm²/min, respectively. In the experiment pH, protein content and volume of saliva were also measured (values not given) and according to authors there was no influence from pH and protein content of the saliva on the migration rate.

Steiner et al. (1998) found average migration rates of DINP (1.4 μg/10 cm²/min) and DEHP (0.4 μg/10 cm²/min) released during sucking on PVC sheets containing 32% DEHP or 36% DINP.

Chen (1998) measured the migration of DINP from disks of five different toys in two test persons for 4 time periods. The average migration rate of DINP for all time periods for individuals ranged from 1.1 to 9.9 μg/10 cm²/min.

It should be mentioned that the released phthalates from the toy might be hydrolysed by saliva forming monoesters of released phthalates. These monoesters are not included since only the parent compounds (diesters) in the saliva have been measured.

24 DINP containing toys (12.9 to 39.4% DINP) have been tested in a dynamic in vitro method (“head-over-heels”) and migration rates ranged from 1 to 11.1 μg/10 cm²/min with a mean migration rate of 4.1μg/10 cm²/min (Simoneau et al. 2001 – as quoted in Babich et al. 2004).

In another “head-over-heels” study, 14 DEHP containing products (3-45%) were included. The migration rate of DEHP ranged from 0.3 – 5.2 μg/10 cm²/min with a mean of 1.8 μg/10 cm²/min. The migration of DINP was at the same level (Bouma et al. 2002).

The content of DINP and DEHP in the products investigated is at the same level as the content found in pet toys (Nielsen et al. 2005A). However, not only plasticizer content but also other parameters of the product (e.g. surface roughness, coating type, thickness) influence the release (Bouma et al. 2002). It is also very likely that dogs chewing and biting result in more mechanical agitation of the products compared to humans and thereby to a higher release of phthalates. Differences in saliva (quality, amount and destiny (ingestion vs slavering)) could also influence the migration rate. Furthermore, we have no information on the migration of phthalates in contact with gastrointestinal fluid that e.g. has a lower pH, a higher fat content and contains other enzymes than saliva. However, it will be necessary to assume that the migration rate measured by either in vivo or in vitro extraction methods resemble the migration in dogs during biting and chewing on the toy as well as the migration from the toy while in the gastrointestinal tract.

Overall, the migration rate of DINP range from 0.3 μg/10 cm²/min to 11.1 μg/10 cm²/min. To cover the whole range of migration rates the minimum, an average value from Kùnemann (1998) as well as the maximum migration rate (0.3, 2.44 and 11.1 μg/10 cm²/min respectively) will be used as examples in the exposure estimations.

Regarding the migration of DEHP there are fewer investigations than of DINP. However minimum, mean and maximum migration rates (0.3, 1.8 and 5.2 μg/10 cm²/min, respectively) measured by the in vitro extraction method will be used in the assessment.

2.4 Duration of gastrointestinal passage in dogs

The duration of the gastrointestinal passage in dogs is not a fixed parameter as it differs with e.g. the composition of food and food particle size. However, in general it ranges from 12-30 hours. A value of 24 hours will be used as the duration of the gastrointestinal passage, i.e., the exposure duration. The exposure duration of 24 hours includes both the time where the dog chews and bites in the toy as well as the time pieces of toy is retained in the gastrointestinal tract.

2.5 Body weights of dogs

The body weight of dogs depends off course on strain and age. In general it ranges from 1 kg to 40 kg and values of 1, 5, 10, 20 and 40 kg will be used in the exposure estimations.

2.6 Estimating the exposure

Two different ways to estimate the exposure will be performed. The estimations will either be based on A) a measured migration rate or B) the assumption that 10% of the phthalate present in the toy migrate while in the gastrointestinal tract.

2.6.1 Estimation A - based on measured migration rate

It will be assumed that a dog chews and bites and swallows a piece of toy with a given area (1, 5, 10 and 50 cm²) and as mentioned previously that the duration of chewing and biting as well as time the product is retained in the gastrointestinal tract is 24 hours in total.

The exposure can be estimated as:

Worst-case exposure estimations are based on the maximum migration rate (5.2 and 11.1 μg/10 cm²/min for DEHP and DINP, respectively) and average exposure estimations on the average rate (1.8 and 2.44 μg/10 cm²/min for DEHP and DINP, respectively).The estimated exposures of DEHP and DINP for dogs weighing from 1 to 40 kg, eating from 1 to 50 cm² of toy is presented in Table 2A and 3A. See Appendix 2 for further details.

2.6.2 Estimation B - based on 10% (w/w) migration of phthalate

It will be assumed that a dog has swallowed a piece of toy with a given mass (1, 5, 10 and 50 g) and that 10 % of the phthalates present in the product migrate while in the gastrointestinal tract (24 h).

The exposure can be estimated as:

Worst-case exposure estimations are based on maximum contents (39% DEHP and 54% DINP) and average exposure estimations on average contents (21% DEHP and 27.5 % DINP). The estimated exposures of DEHP and DINP for dogs weighing from 1 to 40 kg, eating from 1 to 50 g of toy is presented in Table 2B and 3B. See Appendix 1 for further details.

Table 2. Estimated exposures of DEHP for dogs weighing from 1 to 40 kg, eating 1, 5, 10 or 50 g or cm² of product and using either migration rate (A) or the assumption that 10% of the phthalate in the toy migrate while in the gastrointestinal tract (B) to estimate exposure.

Table 3. Estimated exposures of DEHP for dogs weighing from 1 to 40 kg, eating 1, 5, 10 or 50 g or cm² of product and using either migration rate (A) or the assumption that 10% of the phthalate in the toy migrate while in the gastrointestinal tract (B) to estimate exposure.

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Version 1.0 August 2006, © Danish Environmental Protection Agency