Based on the information provided, the best strategy to mitigate the pollution effects from the millions of cars in Los Angeles would be a government controlled effluent standard. Tradable permits and pollution taxes are market-based solutions that rely on individuals or businesses to voluntarily participate in trading or paying a tax to reduce emissions. However, since the millions of people commuting may not have strong interests in trading, a government controlled effluent standard would set a mandatory limit on emissions and hold all businesses and individuals accountable for reducing their pollution output. This would ensure that everyone is doing their part in reducing emissions and mitigating the pollution effects in Los Angeles.