| Front page | | Contents | | Previous | | Next |

Emission of chemical substances from products made of exotic wood

3 Materials

• 3.1 Allergic Symptoms caused by the Content and the Emission of Chemical Compounds from Exotic Wood Species
• 3.2 Selection of Products
• 3.3 Determination of Wood Species
  • 3.3.1 Sheesham
  • 3.3.2 Belalu

3.1 Allergic Symptoms caused by the Content and the Emission of Chemical Compounds from Exotic Wood Species

From the literature numerous wood species are known, which can cause different symptoms in humans. In far the most cases the symptoms reported have, however, occurred in connection with processing of the wood, e.g. sawing or sanding. Exposure during processing is often many times larger than by general use of the products. Exposure can in this connection take place by inhalation of the compounds emitted, inhalation of dust and by skin contact with wood and wood dust.

Quite comprehensive surveys are available with identification of a number of compounds, which can cause allergy (Hausen, 1981; Woods and Calnan, 1976; Turjanmaa et al., 2002). These compounds have almost all of them a large molecular weight, and only in rare cases these compounds are expected to emit from the wood and usually it is expected that it is impossible to demonstrate these compounds by headspace analysis.

Far the most frequent reason for health effects by processing of wood is due to unspecified, irritative reactions caused by wood dust, which both can cause irritation of skin and the mucous membranes of the airways. These symptoms can in most cases be avoided by use of gloves, safety clothing and exhaust. Persons, who have developed allergy, will in future react to even very low exposure, and exhaust, usual safety clothing etc. will often not be adequate.

When the wood gives rise to allergic reactions it is either due to direct contact to intact wood through contact of the finished product, or – almost always – exposure to wood dust, which is produced during processing. The wood dust will of course contain the same proteins and chemical compounds as the wood itself, but due to the size of the particle, these compounds will be air borne and thereby the persons processing the wood will be exposed to dust both on the skin and in the mucous membranes – also even though they avoid direct contact with the wood specimens.

No information is available as to how frequent different wood species cause biological reactions in woodmen, sawmill workers, and persons processing the wood or users. Most literature information concerns individual cases.

Real epidemics are described in connection with new wood species with unknown allergen potential have substituted well-known wood species such as Pao Ferro (Conde-Salazar et al., 1980; Hausen, 1982).

Patients with eczema caused by wood dust often at the same time have respiratory symptoms (Estlander et al., 2001). A Danish examination (Schlünssen et al., 2002) of 2423 workers in the wood industry concludes that wood dust seems to be able to cause airways symptoms predominantly on irritative basis in spite of a relatively low exposure. Correspondingly, chronic bronchitis is described as a frequent pulmonary disease in wood workers exposed to wood dust. (Enarson and Chan-Yeung, 1990).

In numerous cases the reaction is not due to allergens from the wood itself, but from mould etc. growing on the wood as e.g. described by Halpin et al. (1994), or caused by Frunallaria (lichen species), which grows on the bark (De Corres, 1984). Contact eczema can also be caused by compounds added to wood preservatives or in connection with surface treatment, glue or the similar (Wilkinson, 1979; Stoke, 1979; Johnson et al., 1983; Liden, 1990).

The symptoms of this survey have been divided into symptoms from the airways (1+2), symptoms from skin (3+4+5) and general symptoms (6) (Woods, 1976; Hausen, 1981; Hausen, 2000):

1. Respiratory symptoms with asthma and hay fever (rhino-conjunctivitis) and chronic bronchitis.

2. Other specific respiratory symptoms with effect on the general condition such as allergic pneumonia (allergic alveolitis) (Bendtzen et al., 2000), organic dust toxic syndrome (Seifert et al., 2003).

3. Irritation or urticaria by direct skin contact (contact urticaria).

4. Eczema. An eczema reaction consists of tiny vesicles in the skin, redness of the skin, peeling, cracks, callosity and pruritus. The reaction occurs when in direct contact with the causing agent. The eczema is, therefore, designated "contact eczema". Both irritative and allergic contact eczema is known, see below.

5. A special form of plant reaction, closely related to contact eczema is the "Erythema like - multiform reaction", where larger vesicles may occur on the skin at the spot of contact (Goh, 1992).

6. Other reactions, especially cancer and general reactions (due to toxic compounds in the wood) (Hausen, 1981; Woods, 1976; Wills, 1982).

Biological mechanisms:

The cause of skin and respiratory reactions can be:

There are different allergic mechanisms (Bendtzen, 2000):

1. Exposure to protein (albumen) results in an antibody reaction with symptoms consisting of asthma, urticaria and hay fever and in rare cases allergic shock (anaphylactic shock). Not all symptoms should necessarily be present. The asthma, urticaria and hay fever occur immediately after exposure to the allergen (minutes) and the reaction diminishes in a few hours. Skin contact to the allergen protein can in some cases cause localised urticaria (contact urticaria) only at the contact spot, but it can also develop into generalised urticaria, asthma etc. (reactions of this kind are designated the allergic immediate reaction, type-I reaction or mediated by IgE-antibody). Localised urticaria can also be produced without immunological processes by irritation.
2. In certain cases exposure to proteins causes formation of an antibody of the IgG-type. The formation of specific IgG-antibodies can result in allergic pneumonia (alveolitis), which occurs as symptoms of pneumonia up to 1 day after exposure to the allergen.
3. Exposure to numerous chemical compounds can result in an allergic contact eczema. Eczema is not developed until 1-3 days after exposure and it will not diminish until weeks after the exposure has stopped. Eczema never develops into asthma. This type of allergic reaction is designated "mediated allergic reaction" or "delayed cutaneous hyper-sensitivity reaction" or type-IV reaction.

In Table 9 reported symptoms caused by the wood species mentioned in Tables 3, 4 and 7 are stated. It should be noted that the products mentioned in Tables 3, 4 and 7 could be surface treated, which can encapsulate the components of the wood. In stead the surface treatment can be determining for the emission of compounds.

Table 9 Symptoms caused by exotic wood species (Hausen, 1981)

Some of the wood species mentioned in Table 9 are in Denmark used for kitchen table tops and could in this connection get into direct contact with food. It has, however, been impossible to retrieve information about potential problems in this context. A project on application of wood in the food industry (NIF, 1998) for e.g. chopping boards or pallets only comprised "non-exotic" wood species and thus it does not inform about wood species covered by this project.

Allergen proteins are well-known in the sap from rubber tree Hevea brasiliensis, and is extensively described in the literature in connection with rubber products made of natural rubber latex from this wood species (Turjanmaa et al., 2002), but there are no publications about asthma in persons processing wood or reactions caused by contamination of food by contact with products made of wood from Hevea brasiliensis.

3.2 Selection of Products

The experimental part of this project comprises an examination of 10 selected products made of exotic wood. The products partly represent product groups, which in the market survey were found on the market, and partly wood species, which extensively are used for these product groups.

The selected products/wood species can, however, only be considered as representative examples, and they are thereby not covering for all consumer products made of exotic wood on the Danish market in 2003.

The selected products are listed in Table 10.

Table 10 Selected products

* Products, which are normally oil treated, but which in this survey, form part as untreated

** The distributor has informed this product to have been wax treated. It has, however, been evaluated to be lacquered.

The products have as for the majority been examined with the surface treatment, with which they normally appear with the consumer. As for normally oil treated products, when possible products have been bought, which have not been oil treated. This does not represent a typical use situation, but on the contrary it gives a better picture of the chemical compounds emitted from the wood itself. Notoriously, an oil treatment emits numerous compounds, which might conceal the emission from the wood itself.

On basis of the results from an initial qualitative screening (described in paragraph 4.1) of the emission from the 10 products listed in Table 10, 5 products were selected for further quantitative analysis of the emission. The 5 selected products are listed in Table 11.

Table 11 Products selected for quantitative analysis of the emission

The selection of these 5 products is based on the following criteria:

• products, which are used on large surfaces
• products, which emit the most
• products, which are most widely used
• the type of emission from the product

The knowledge of the amount used by the individual wood species is limited. The primary criteria for the selection have, therefore, been products, which form part with a large surface in a typical home and/or has a "high" emission.

The quantitative analysis of emission is described in paragraph 4.2.

3.3 Determination of Wood Species

For two of the selected products made of exotic wood, the distributor/importer has only been able to inform the trade name of the wood species. As the trade name can be geographically determined and vary from area to area, it is necessary to know the botanical name to identify the wood species unambiguously.

Below the determination of the botanical names of the two wood species are listed. Regular descriptions of wood species are for all 10 selected wood species listed in Appendix B (Danish Technological Institute, 2003).

3.3.1 Sheesham

Among the selected products there is a bed table made of the wood species sheesham. The bed table is part of a series of furniture, distributed via Idé Møbler.

At purchase of the table with the distributor the wood species had different designations in the catalogue, product descriptions and price tags e.g. sesame, shesam, sheesam.

Neither the distributor nor the importer could inform the botanical name of the wood species but referred solely to the trade name.

On basis of samples taken from the purchased piece of furniture the wood species has subsequently been tried determined via a literature study. The major part of the wood used in the piece of furniture in question is sapwood, which makes a unique determination of species impossible. It is either Dalbergia latifolia or D. sissoo. These two wood species can only be determined by difference in colour and not by microscopic characters. As the wood material in question primarily consists of juvenile wood, the colour is less characteristic. It is, therefore, impossible with certainty to determine the wood species, but there is every probability that it is Dalbergia latifolia (Venås, 2003). This identification is used with the above-mentioned reservations throughout this report.

3.3.2 Belalu

A figure cut of an Indonesian wood species named belalu forms part of the project. The importer, who personally is in charge of the purchase of the figures in the country of origin, can only inform the Indonesian name, belalu, of the wood species.

From the name belalu there is every probability that it is the wood species with the botanical name Albiz(z)ia falcata, which in Danish, English and German is named batai (Venås, 2003). This corresponds to the literature description of the appearance and structure of the wood and to its application for woodcarving with a low degree of detailing. In the present report it is, therefore, assumed that it is Albiz(z)ia falcata.

| Front page | | Contents | | Previous | | Next | | Top |

Version 1.0 September 2005, © Danish Environmental Protection Agency