Formaldehyde

Toxicity to terrestrial plants

Description of key information

In accordance with Annex IX of Regulation (EC) No 1907/2006, the equilibrium partitioning method has been used for assessing the hazard to soil organisms.

Additional information

Reliable studies on the short and long term toxicity of formaldehyde to plants are available. These studies are reliable, however they were not performed according to current guidelines and therefore not been considered for the derivation of PNECsoil. In accordance with Annex IX of Regulation (EC) No 1907/2006, the equilibrium partitioning method has been used for assessing the hazard to soil organisms.

Short term toxicity to plants:

A 5 h exposure to formaldehyde at 0.44 mg/m3 (0.37 ppm) resulted in a significant reduction in pollen-tube length, whereas a 1 or 2 h exposure was innocuous. When the formaldehyde concentration was increased to 2.88 mg/m3 (2.4 ppm), a 1 h exposure caused a decrease in tube length (Masaru et al., 1976).

The most sensitive effect for terrestrial organisms resulting from exposure to formaldehyde in air was an increase in the growth of shoots, but not of roots, of the common bean (Phaseolus vulgaris) after exposure to average measured concentrations of 78, 128, 239 and 438 μg/m3 in air (day: 25°C, 40% humidity; night: 14°C, 60% humidity) for 7 hours per day, 3 days per week, for 4 weeks, beginning at the appearance of the first macroscopic floral bud, 20 days after emergence (Mutters et al., 1993). Although the authors concluded that there were no short-term harmful effects, it has been suggested that an imbalance between shoot and root growth may increase a plant’s vulnerability to environmental stresses such as drought, because the root system may not be large enough to provide water and nutrients for healthy plant growth (Barker & Shimabuku, 1992).

Long term toxicity to plants:

Effects on plants were also studied following exposure to formaldehyde in fog water. Seedlings of winter wheat (Triticum aestivum), aspen (Populus tremuloides), rapeseed (Brassica rapa) and slash pine (Pinus elliotti) were exposed to formaldehyde concentrations of 0, 9000 or 27 000 μg/L in fog for 4.5 hours per night, 3 nights per week, for 40 days. Based on an unspecified Henry’s law constant, calculated corresponding atmospheric gas-phase formaldehyde concentrations were 0, 18 and 54 μg/m3, respectively. In rapeseed grown in the formaldehyde fog, significant (p ≤ 0.1) reductions in leaf area, leaf dry weight, stem dry weight, flower number and number of mature siliques (seed pods that produce seed) were observed compared with control plants. The slash pine showed a significant increase in needle and stem growth. No effects were observed in the wheat or aspen at test concentrations (Barker & Shimabuku, 1992).