Review
Plastics additives in the indoor environment—flame retardants and plasticizers

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Abstract

Phthalic acid esters and phosphororganic compounds (POC) are generally known as semivolatile organic compounds (SVOCs) and are frequently utilized as plasticizers and flame retardants in commercial products. In the indoor environment, both compound groups are released from a number of sources under normal living conditions and accumulate in air and dust. Therefore, inhalation of air and ingestion of house dust have to be considered as important pathways for the assessment of exposure in living habitats. Especially in the case of very young children, the oral and dermal uptake from house dust might be of relevance for risk assessment. A critical evaluation of indoor exposure to phthalates and POC requires the determination of the target compounds in indoor air and house dust as well as emission studies. The latter are usually carried out under controlled conditions in emission test chambers or cells. Furthermore, chamber testing enables the determination of condensable compounds by fogging sampling. In the case of automobiles, specific scenarios have been developed to study material emissions on a test stand or to evaluate the exposure of users while the vehicle is driving.

In this review, results from several studies are summarized and compared for seven phthalic esters and eight POC. The available data for room air and dust differ widely depending on investigated compound and compartment. Room air studies mostly include only a limited number of measurements, which makes a statistical evaluation difficult. The situation is much better for house dust measurements. However, the composition of house dust is very inhomogeneous and the result is strongly dependent on the particle size distribution used for analysis. Results of emission studies are presented for building products, electronic equipment, and automobiles.

Daily rates for inhalation and dust ingestion of phthalic esters and POC were calculated from 95-percentiles or maximum values. A comparison of the data with results from human biomonitoring studies reveals that only a small portion of intake takes place via the air and dust paths.

Introduction

From a chemical point of view, plastics are understood to be materials which essentially consist of synthetic or naturally based macromolecular organic compounds. More than 10 million tons per year of plastics are produced in Germany, the share of PVC being approx. 1.2 million tons (Pohle, 1997). The versatile applications of plastic products have earned them an overriding importance on the market throughout the world. To achieve the desired material properties, additives are added to plastics, depending on the field of application. These serve for an intended influencing of mechanical properties (e.g., plasticizing), for stabilization against ageing effects (e.g., the effect of light), and safety aspects (e.g., fire protection). As far as the quantity and the current relevance of environmental matters is concerned, the phthalates (phthalic acid esters) used as plasticizers and the organophosphate-based flame retardants constitute the major part of plastics additives.

Flame retardants is a collective term for such inorganic and/or organic substances which make especially plastics, wood, and wood-based materials as well as textiles flame-proof (Umweltbundesamt, 2000). The phosphororganic compounds (POC) have great importance for indoor products. Table 1 provides a compilation of the most usual agents. For reasons of safety, the use of flame retardants is necessary in many products. Detailed information about the possible effects of an application is required to be able to estimate the health impact of such products in the indoor environment. This especially concerns the release of flame retardants in the indoor environment under normal conditions of use and living. Many flame retardants currently used are classified as hazardous substances or must be regarded as potentially hazardous to health, so that possible health impairments following inhalative, oral, or dermal intake must be evaluated (WHO, 1997b).

For this reason, an indoor guideline value RW I of 0.005 mg m−3 for tris(2-chloroethyl)phosphate (TCEP) and some other organophosphate-based flame retardants was suggested (Sagunski and Roßkamp, 2002). A further risk assessment also requires reliable data on the release of flame retardants under real conditions of use. As early as in 1980, Weschler has pointed to the release of organophosphoric esters in indoor environments. However, it was only in the 1990s when systematic studies were carried out regarding the presence of organophosphoric esters in the indoor air (Carlsson et al., 1997, Sjödin et al., 2001, Sagunski et al., 1997, Ingerowski et al., 2001). Measurements of household dust have also revealed the presence of various organophosphoric esters (Ingerowski et al., 2001, Hansen et al., 2001, Pardemann et al., 2000, Kersten and Reich, 2003, Nagorka and Ulrich, 2003).

Today, phthalates are added to plastics in order to achieve the desired plasticizing properties. Phthalates count among the omnipresent environmental chemicals in water and soil, but rarely occur in the air due to their low volatility (WHO, 1992, WHO, 1997b, Umweltbundesamt, 1999, Staples, 2003). Potential emission sources of phthalates in indoor environments include wall coverings (Uhde et al., 2001), wall paints, floor coverings (Wilke et al., 2003), and electronic devices (Wensing, 1999a, Wensing, 1999b, Wensing, 2001). Since building products applied to walls and floors sometimes add up to a considerable portion of a room's surface, they may constitute a relevant source of phthalates. The soft PVC preferably used in wall coverings may contain more than 30% of phthalic acid esters. Until the end of the nineties, the compounds mainly used in PVC were DBP, DIBP and DEHP, whereas today DINP (for abbreviations, see Table 1) is of increasing importance in PVC products (Pohle, 1997, Lorz et al., 2002). Several phthalates and especially DEHP are suspected of having carcinogenic and teratogenic effects. Moreover, toxic effects regarding development and reproduction are discussed controversially (Kahl et al., 2003, Koch et al., 2003a, Koch et al., 2003b, David, 2004, Bornehag et al., 2004, Cadogan, 1999). Phthalates are often referred to as “fogging-active” substances and are suspected of contributing to the Black Magic Dust phenomenon (Moriske et al., 2001).

The assessment of the exposure of persons in indoor environments towards POC and phthalates requires determining a large number of analytic parameters. Furthermore, the individual living conditions must always be taken into account. Gathering data and evaluation of available data allow an assessment which is the subject of this paper.

Section snippets

Exposure scenarios in the indoor environment

A precautionary strategy aiming at avoiding the exposure to indoor pollutants must focus on the control of potential emission sources. A carefully directed production of low-emission products can make an important contribution to reaching this goal. Many products today are subject to regular quality inspections concerning their release of VVOC (Very Volatile Organic Compounds) and VOC (Volatile Organic Compounds). The specific emission rates (SERs) of these compounds which cover a boiling range

Analysis of ingredients

The determination of ingredients is the simplest type of material examination resulting in a general detection of plastics additives such as POC and phthalates using extraction methods. However, the result of this examination does not allow drawing any conclusions regarding a possible exposure towards the components detected here. The additives may be bound so firmly into the plastic matrix that there is no or only very low release under normal conditions of use. However, the extraction

Field measurements, test chamber, and dust measurements

Only few studies regarding the emission behavior of phthalates are known up to now. In 1996, studies were carried out on PVC products in test chambers under defined conditions (Thölmann, 1996). At room temperature, the DEHP concentration was less than 0.1 μg m−3. At higher temperatures, the values in the test chamber increased as was expected. The maximum value at 60 °C was 5.2 μg m−3. Wilke and Jann (1999) have described test chamber studies of wall coverings containing DEHP. In tests over a

Parameters for risk assessment

Parameters, which are substantiated from a toxicological point of view, are required for interpreting the exposure data and for risk assessment. These parameters usually are transferred from animal experiment studies to humans. In this context, NOEL (No Observed Effect Level) designates the dose which results in no impairment when the exposure is chronical. However, the NOAEL (No Observed Adverse Effect Level) only considers the impairing effects or their absence. NOAEL therefore is higher than

Conclusions

The assessment of the exposure of persons towards plastics additives (plasticizers and flame retardants) requires reliable measuring data. When gathering such measuring data for phthalates and phosphoorganic compounds (POC) and evaluating them, the special physical properties of these compounds as well as the conditions of indoor use must be taken into account in indoor air, household dust, and test chamber measurements (Wensing and Salthammer, 2002).

Various authors have gathered and

Acknowledgement

The authors are grateful to the Dr.-Michael-Rosenthal Foundation, Lingen, Germany for financial support.

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