Factors Affecting Transfer of Pyrethroid Residues from Herbal Teas to Infusion and Influence of Physicochemical Properties of Pesticides

Abstract

The transfer of pesticide residues from herbal teas to their infusion is a subject of particular interest. In this study, a multi-residue analytical method for the determination of pyrethroids (fenpropathrin, beta-cypermethrin, lambda-cyhalothrin, and fenvalerate) in honeysuckle, chrysanthemum, wolfberry, and licorice and their infusion samples was validated. The transfer of pyrethroid residues from tea to infusion was investigated at different water temperatures, tea/water ratios, and infusion intervals/times. The results show that low amounts (0-6.70%) of pyrethroids were transferred under the different tea brewing conditions examined, indicating that the infusion process reduced the pyrethroid content in the extracted liquid by over 90%. Similar results were obtained for the different tea varieties, and pesticides with high water solubility and low octanol-water partition coefficients (log K_ow) exhibited high transfer rates. Moreover, the estimated values of the exposure risk to the pyrethroids were in the range of 0.0022-0.33, indicating that the daily intake of the four pyrethroid residues from herbal tea can be regarded as safe. The present results can support the identification of suitable tea brewing conditions for significantly reducing the pesticide residue levels in the infusion.

Keywords: herbal tea; infusion; pyrethroids; risk assessment; transfer.

Figure 1

Effect of water temperature on the transfer ratio (defined as the ratio of the amounts of residues in tea and water) of the four pyrethroid residues from wolfberry (a); licorice (b); honeysuckle (c); and chrysanthemum (d) tea leaves to infusion.

Figure 2

Effect of infusion interval on transfer ratios of the four pyrethroid residues from wolfberry (a); licorice (b); honeysuckle (c); and chrysanthemum (d) tea to infusion.

Figure 3

Effect of infusion time on the transfer ratios of the four pyrethroid residues from wolfberry (a); licorice (b); honeysuckle (c); and chrysanthemum (d) tea to infusion. Missing white bars denote that no corresponding residues were detected in the third infusion.

Figure 4

Effect of tea/water ratio on the transfer ratios of the four pyrethroid residues from wolfberry (a); licorice (b); honeysuckle (c); and chrysanthemum (d) tea to infusions. Different minor case letters (a, b) at the top of the columns mean significant differences of transfer ratio at a p value of 0.05.

Figure 5

Relationship between water solubility (log Ws) (a) or partition coefficient (log Kow) (b) and the transfer rates of pesticides during tea brewing. The F1, L, B, and F2 labels in the figure represent fenpropathrin, lambda-cyhalothrin, beta-cypermethrin, and fenvalerate, respectively.