… is from page 257 of Julian Morris’s 2002 essay “Epilogue: What is sustainable development and how can we achieve it?” which is the final chapter in Sustainable Development: Promoting progress or perpetuating poverty?  (Julian Morris, ed. ) (footnote excluded):
As Robert Bradley noted in chapter 10, the environment has also improved dramatically over the course of the past century in developed countries, with significant declines in air and pollution. The air in London is now cleaner than at any time since the sixteenth century! And even indoor air pollution – arguably among the biggest causes of early death among the world’s poor – is improving, as people in poor countries switch from poorly flued wood and dung fires to using gas and electricity, or simply better, more efficient stoves. But these changes are only possible with increases in income, which enable the purchase of superior technologies and encourage people to spend money on more efficient goods because their time is no longer efficiently spent gathering wood and dung for fuel.