70 livro de ficção científica onde a Terra se tornou tão poluída, as pessoas usam máscaras de gás do lado de fora; os cientistas encontram uma solução temporária ao expandir a atmosfera

Como sobre o O Carneiro Look Up por John Brunner. Publicado em 1972 e nomeado para uma nebulosa. Caiu fora da impressão, mas parece estar disponível novamente.

Na página da Amazon :

An enduring classic, this book offers a dramatic and prophetic look at the potential consequences of the escalating destruction of Earth. In this nightmare society, air pollution is so bad that gas masks are commonplace. Infant mortality is up, and everyone seems to suffer from some form of ailment. The water is polluted, and only the poor drink from the tap. The government is ineffectual, and corporate interests scramble to make a profit from water purifiers, gas masks, and organic foods.

Environmentalist Austin Train is on the run. The Trainites, environmental activists and sometime terrorists, want him to lead their movement. The government wants him in jail, or preferably, executed. The media wants a circus. Everyone has a plan for Train, but Train has a plan of his own.

Aqui está outra possibilidade - "Population Doomsday" (1970), de Don Pendleton. Eu nunca li isso, mas lembro que a capa tinha um homem com uma máscara de gás.

De esta análise da Amazon :

It's January 1989 and a new President, Royal Hackett, takes office in the midst of an eco-catastrophe. The population of the US has reached 390 million and there is widespread environmental degradation. Air pollution in the cities is so bad that people are obliged to wear gas masks when out-of-doors. The rest of the world is in as bad a shape (or worse).

The main character is a reporter named Bill Vance, who knows the President well enough to be invited to attend White House planning sessions on measures to address the national dilemma. Vance soon finds himself sent to Gary, Indiana, where a disastrous smog event has left most of the city's population dead or dying. The scenes in which Vance, attired in a cumbersome space suit, wanders the darkened streets of the city only to see mounds of the gasping dying, are effective.