Starting with your introduction, I would incorporate a definition of asthma and a description of symptoms. Are there different sub-types that should be discussed here? What are the consequences/implications of asthma? I would also report general prevalence of asthma, and any changes in prevalence over the last decade or so (if notable). After establishing this background, then I would get in to what you have here to establish the presence of a disparity that is worth exploring with a literature review. I am also a bit confused by your first CDC citation- is that the title of the web page? You may be able to truncate this to (CDC, 2019). I would also consider revising your research question for clarity- something along the lines of ‘what factors contribute to the elevated prevalence of asthma in adolescents living in urban environments in the United States?’ (lung function is a very broad term, and I think specifying your interest in asthma here will help remove any confusion for your reader).
For your methods, with 10 searches you should absolutely consider a table to keep track of these and avoid heavy repetition in your methods section. Even if you have identical inclusion/exclusion criteria for every search this would be a lot to cover long-form. You are also missing some key details here. You should report the size of the pool of results with just search terms, and after applying your filters for publication date and peer reviewed literature. You need to report how many articles you ultimately included in your paper from each search, and what your process was for sorting through the articles in your final results pool to identify those articles you wanted to include. You may have looked at every title/abstract and then selected articles to read further from there- whatever your process was you need to report it. See the examples on ELC for guidance on structuring a methods table/how to write up and report your search strategy.
As for your results, you need to get some thematic organization going here. Looking through your citations I see several that address outdoor/traffic-related air pollution- this would be a good theme. You also talk about housing-related exposures (pestilence, indoor smoke), another good potential theme. For your third theme, you might consider looking at differences in how asthma is treated in urban settings, or identify some other common thread as you read more literature. Regardless of what themes you land on, you should organize your presentation of results in this way to help with readability and to ensure you are not repeating yourself over the course of your results section.
You have a lot going on in your discussion. Typically this section is structured as a brief synthesis of your results (do not reuse citations, and do not restate what you have already said in the results), followed by a discussion of the limitations of your review and then some coverage of solutions to the issues you highlighted previously. Is a policy-level change the most appropriate course of action? Are any of those risk factors you identified manageable through education, or are there specific programs dedicated to reducing the presence of those risk factors? See what is being done in this field and what might help improve this disparity.
