KANBrief 3/21

Permethrin in PPE for protection against tick bites

People working in hunting, forestry or in some other capacity in forests, and also employees of road maintenance services and the armed forces, are exposed to an elevated risk of tick bites at work. One form of prevention for this group of people is the wearing of work clothing with built-in protection against ticks. Clothing treated with permethrin is used in particular for this purpose.

Permethrin is an active biocidal agent used to protect against parasites, in particular against ticks. When clothing has been impregnated with permethrin during the manufacturing process, it serves as personal protective equipment (PPE) against ticks. The biocide is applied to the clothing by spray treatment, immersion in aqueous emulsions, polymer coating of the fibres during manufacture or micro and nano-encapsulation.

The active substance can however be released from the clothing on contact with the skin and absorbed through the latter. Prolonged body contact and external conditions such as humidity, temperature, perspiration and the material properties of the textiles can influence absorption. Permethrin is classified under CLP Regulation (EC) No 1272/2008 as a Category 1 skin sensitizer with hazard statement H317 (“May cause an allergic skin reaction”). In the EU, permethrin is considered non-carcinogenic based on the results of tests of active agents in accordance with the Biocide Regulation (EU) No 528/2012.

Draft standard with controversial requirements

In March 2020, the first draft standard on this subject was published: EN 17487, Protective clothing – Protective garments treated with permethrin for the protection against tick bites. The standard describes requirements and tests of clothing treated with permethrin for protection against tick bites (even after a defined number of washes under specified washing conditions). At the same time, the draft standard asserts that the clothing described in it is “harmless” to wearers of the clothing.

According to the draft, the mean permethrin content of finished garments must not exceed 1,600 mg/m² of textile, with a maximum inhomogeneity of 20 %. This would permit local concentrations of permethrin of over 1,900 mg/m². Studies into the health protection of users of textiles treated with permethrin (e.g. [1], [2], [3]) have generally been conducted at permethrin levels of 1,250 mg/m² of textile. According to the WHO recommendation4, the recommended dosage for coats, jackets, long-sleeved shirts and trousers is 1,250 mg/m² and for short-sleeved shirts only 800 mg/m². The value stated in the draft standard is thus significantly higher than the recommended concentrations.

Germany opposed the high permethrin value in the 2020 public enquiry. Firstly, no information is available on whether such a concentration is necessary (or is being promoted merely because of processes currently used by some manufacturers); secondly, it is unclear whether this concentration could in fact have harmful effects on workers who wear the clothing for longer periods. A second draft standard, which still includes the high value, is currently at the public inquiry stage.

The draft standard also addresses requirements for the protection of users. Reference is made here to the ADI (accepted daily intake) value of the WHO. According to the draft, “it is expected that the 20 % ADI is not exceeded during common professional use of the garments when covering the lower and upper body (torso, arms and legs) during an 8-h working day. In case of longer use, for example for 24 h a day, at most 60 % of the ADI will be reached”.

However, the means by which the permethrin is bound in the textile, which in turn is a consequence of the treatment method, is particularly relevant. Annex E of the current draft standard states that “if the permethrin is not firmly bound to the fabric, then the ADI for permethrin can be exceeded, especially when the starting concentration of permethrin is close to the maximal permethrin content in fabrics formulated in this document”. Furthermore, the standards working group points out in clause E 10.4 that no standardized methods exist by which the health effects of permethrin could be reliably assessed.

The draft standard therefore leaves questions unanswered. In principle, there are advantages to standardizing test methods for PPE treated with permethrin. It would be important for the impregnation methods also to be standardized and knowledge thereby gained of the extent to which they influence the release rate and thus the intake by humans under a range of conditions. Only then would risk assessment really be possible. Until this is achieved, the permissible mean concentration at impregnation should not exceed 1,250 mg/m², consistent with the requirement for exposure to be kept to a minimum and owing to the limited scientific knowledge.

Dr. Anja Vomberg

Dr. Michael Thierbach

1 K.E. Appel et al., Risk assessment of Bundeswehr (German Federal Armed Forces) permethrin-impregnated battle dress uniforms (BDU). Int J Hyg Environ Health. 2008,
2 B. Roßbach et al., Abschlussbericht “Biomonitoring und Beurteilung möglicher Gefährdungen von Beschäftigten in der Forstwirtschaft durch permethrinimprägnierte Schutzbekleidung“, Institut für Arbeits-, Sozial- und Umweltmedizin der Universitätsmedizin Mainz; ca. 2012 www.dguv.de/projektdatenbank/0305/12_11_23_abschlussbericht_permethrin_final.pdf
3 BfR: Allergien: Sensibilisierung durch Permethrin in Textilien ist unwahrscheinlich, Stellungnahme Nr. 006/2017, www.bfr.bund.de/de/a-z_index/permethrin-4880.html
4 WHO: Vector control – Methods for use by individuals and communities. Prepared by Jan A. Rozendaal 1997

The limit value counts

The view of the Social insurance for agriculture, forestry and landscaping (SVLFG) is that no clear conclusion can be drawn regarding chemical protection against tick bites. The daily risk of tick-borne diseases for the exposed professions has been known for many years. Preventive measures are recommended and complementary measures are being sought. At the same time, it is not acceptable that protective clothing treated with excessive quantities of permethrin presents a health risk to insured individuals. A balance between the two aspects should therefore be sought in the standardization process to determine an appropriate limit.

Sebastian Dittmar, SVLFG