Aims Carbon (C) and nitrogen (N) cycling are key ecosystem functions potentially altered by heavy metal pollution. We used an ecosystem approach to study the long-term effect of lead (Pb) on C and N cycles in a natural grassland in a former shooting range. Methods Microbial activity was evaluated by substrateinduced respiration (SIR) in situ, adding isotopically labelled C 4-sugar to the soil. C and N contents and natural abundance of isotopes were measured in grass leaves, soil and microbial biomass together with root biomass. Results A reduced microbial activity and microbial biomass per area, together with a higher soil C stock and C:N ratio suggested a lower microbial decomposition in high Pb compared to low Pb areas. A more closed N cycle in the high Pb area was indicated by 2-3‰ lower δ 15 N in leaves and soil compared to low Pb areas. Higher δ 13 C in leaves and higher root biomass but similar leaf nutrient contents indicated plant responses and adaptions to the high Pb. Conclusions The applied ecosystem approach revealed that Pb slowed down the C and N cycles, possibly by indirect effects rather than by direct toxicity. The ecosystem seems to have adapted to altered conditions.

Outdoor air pollution inside populated areas is a growing environmental health concern. Epidemiological data related to exposures to outdoor air pollution are limited in rural areas. We previously assessed indoor and personal exposures in two Chinese rural counties, Xuanwei and Fuyuan, where the domestic combustion of locally sourced “smoky” (i.e., bituminous) but not “smokeless” (i.e., anthracite) coal has been associated with the highest lung cancer rates in China. In addition, we have previously reported that improving home ventilation by installing stoves with chimneys was associated with a reduction in lung cancer rates in this region. However, outdoor air pollution from indoor burning of coal and the impact of improving household ventilation on outdoor air pollution have never been assessed in this area. Therefore, we measured outdoor fine particulate matter (PM2.5) and polycyclic aromatic hydrocarbons (PAHs) including the known carcinogen benzo-a-pyrene (BaP) over two consecutive 24-hour sampling periods in 29 villages. Half of the villages were revisited several months after the initial sampling period to repeat all measurements. The overall concentrations of outdoor pollutants in Xuanwei and Fuyuan were 53.1 μg/m3 (13.2-103.4 μg/m3) for PM2.5, and 11.1 ng/m3 (5.9-19.8 ng/m3) for BaP. PM2.5 levels were almost twice as high as the 24-hour mean World Health Organization guideline value of 25 μg/m3. Outdoor BaP concentrations in villages with homes using smoky coal were significantly higher than those with homes that used smokeless coal (11.6 vs 5.9 ng/m3, p < 0.05). Among villages using smoky coal, higher outdoor BaP levels were found in villages where >50% of households had a chimney compared to villages where ≤50% of homes had a chimney (12.3 vs 7.1 ng/m3, p = 0.024). Outdoor PM2.5 was moderately correlated with the indoor concentration (Spearman rs = 0.28, p = 0.011). These results show that outdoor air pollution in a rural region of China with a high incidence of lung cancer was associated with type of coal used for cooking and heating indoors and the presence of stove ventilation. These findings suggest that further reducing adverse health effects in rural villages from home burning of coal will likely require use of stoves that reduce environmental exhaust and/or the replacement of coal with cleaner fuel types. Citation Format: Wei Hu, George Downward, Boris Reiss, Nathaniel Rothman, Jihua Li, Jun He, K.F Morales-Collins, Jun Xu, Weijie Seow, Bryan Bassig, Dean Hosgood, Linlin Zhang, M Hoogeveen, Ingrid Rijk, Guoping Wu, Fusheng Wei, Roel Vermeulen, Qing Lan. Outdoor air pollution and household coal combustion in a rural high lung cancer incidence area of China. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3432.

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