Using charcoal as base material reduces mosquito coil emissions of toxins

Abstract

Mosquito coils are used to prevent mosquito exposures indoors by approximately 2 billion people worldwide. However, the smoldering of organic matters used as base materials of mosquito coils emits particulate and gaseous toxic compounds. A previous study indicates that emission rates of toxic compounds depend on types of base materials and can be high enough to generate room concentrations markedly higher than health based standards or references. The objective of this study is to evaluate a new type of mosquito coil that uses charcoal powder as base material and to compare its emission rates with those of several current-market brands and several brands tested in the previous study. Results show that the charcoal-based coil had emission rates of PM(2.5) mass, total particle number, polycyclic aromatic hydrocarbons (PAH), and aldehydes, substantially (up to 10 times) lower than other tested conventional mosquito coils. Results also show that particles freshly generated from burning mosquito coils were all fine and mostly ultrafine in size. This study presents emission rates for PM(2.5) mass, total particle number, gas-phase and particle-phase PAHs, 14 aldehydes and acetone, and 10 volatile hydrocarbons. These data, along with emission rates presented in the previous study are useful for estimating indoor concentrations of toxic compounds generated from mosquito coil uses. Practical Implications Mosquito coils are widely used indoors to prevent mosquitoes from entering indoor environments. This is achieved through the release of insecticides impregnated in biomass base materials of mosquito coils during coil combustion. A previous study reported that burning one mosquito coil releases the same amount of fine particles as burning 75-135 cigarettes, largely depending on what biomass (saw dust or coconut husk) is used as base material. This 'follow-up' study measured several current-market brands of mosquito coils, including a new charcoal-based coil labeled as smokeless coil by the China Environmental Labeling, for their emissions of particulate and gaseous pollutants. Results show that using charcoal powder as base material reduces fine particle emissions by a factor of 5-10 and also reduces emissions of pollutants such as formaldehyde and PAHs substantially.

Figure 1

Comparison of visible smoke between a charcoal-based smokeless mosquito coil (Lanju Smokeless coil appearing in black) and a sawdust-based conventional mosquito coil (Bison coil appearing in gray)

Figure 2

Schematic diagram of the mosquito coil testing system

Figure 3

Normalized number concentrations of particles emitted from 5 tested mosquito coils as a function of particle diameter