The combination of air pollution and exercise increases the potential problems.
空气污染和运动锻炼加重了潜在的问题。
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The UK-based Royal Commission on Environmental Pollution says that while the materials have so far shown no sign of being harmful, there is a "major gap" in research about their potential risks.
Excess nitrogen and phosphorus nutrients due to large quantities of feed imports, can lead to problems with manure disposal and pose a potentialpollution risk.