What are the environmental and social issues in the City of Ember?

In the novel The City of Ember by Jeanne DuPrau, the major environmental issue facing the City of Ember is the shortage of power. This is emphasized throughout the book. For example, on the Assignment Day, when the mayor gives a cliché speech on encouraging the students to help make the City of Ember more prosperous, Doon complains about the worsening living conditions and frequent blackouts. During Lina’s work as a messenger, she notices a bunch of lights are out. The city experiences a record-long blackout one day, and at the singing event, the lights suddenly go out. In a place where light sources are strictly artificial, power is particularly precious. It's inconvenient enough to be in complete darkness between 9 pm and 6 am; worse still, during daytime, where the lights are supposed to be on, frequent blackouts cause continual panic among the residents. One such example is Lina's worry about losing her two-year-old sister, Poppy, when she is in a shop with her and the lights suddenly go out. It is awareness of the shortage of power that prompts Doon to take the pipeworks job so that he can get close to the power generator and study it, and that is what eventually leads to his finding a way to escape the City of Ember.
There are other environmental issues in the City of Ember, too, implied through certain situations. For example, the shortage of food and “mysterious” death of potatoes in the greenhouse may indicate soil pollution, and the coughing epidemic that took Lina’s father’s life may be caused by air pollution. Biological imbalance may pose another concern, as is shown in the limited plant and bug species in the City of Ember.
The primary social issue in the City of Ember is political. The mayor, leader of the city, is a hypocrite. While telling the citizens to find solutions to improve the conditions in the city, he makes every effort to keep limited and rare resources to himself. He ignores Lina’s letter asking for help to decipher an important message and threatens to imprison the kids for spreading the storeroom scam. Apart from talking, he does little concrete things for the benefit of the city and its citizens. Under such leadership, the only solution is for Lina and Doon to find the way out themselves. Lina does not initially plan to bring her baby sister along, but the mayor’s reaction to the storeroom scam makes her decide to flee with Poppy.