Christchurch City ambient air mutagenicity: A dissertation submitted in partial fulfillment of the requirements for the Bachelors Degree of Science with Honours at Lincoln University

Abstract

The carcinogenic potential of air particles collected from Christchurch, New Zealand were assessed using biological techniques. Ambient air particles less than 10μm in diameter (PM ₁₀) were sampled in summer (January 2001) and winter (May-June 2001) using an Anderson high volume sampler (1640m³ per day) with an attached PM₁₀ inlet. The concentration of particles (μg/m³ ) filtered per day was analysed gravimetrically and chemically. Adsorbed organic components were extracted sequentially for 8 hours with dichlormethane (DCM) and methanol (MeOH) using a soxhlet extraction apparatus. The concentration of airborne particles ranged from 5.59 to 22.94 μgm⁻³ over summer and 14.07 to 165.96 μgm⁻³ during winter. Each filter (representing one day) was analysed for the sixteen polycyclic aromatic hydrocarbons (PAH) recognised by the U.S. Environmental Protection Agency (EPA) as environmentally important, using gas chromatography coupled with mass spectrometry. Both particle weight and PAH concentration were affected by the presence or absence of an inversion layer and daily wind profile. Pooled samples from each of the summer and winter 15-d sampling period were assessed by their ability to mutate DNA (mutagenicity) using th􀁎 Salmonella reversion assay. The S. typhimurium strains utilised were T A98 and TA 100, which contain specific frameshift or base pair mutations within their histidine operon. These were exposed to non-polar and polar extracts in the presence or absence of metabolic enzymes. Non-polar (DCM) winter particle extracts all displayed mutagenic activity; and with the non-polar summer extracts only significant mutagenic to the TA98 strain. Conversely, the summer and winter methanol particle extracts displayed a much lesser mutagenic response. The power of the P AH chemistry data to predict the biological effect will be discussed.