converters.rb

CSV.foreach(file, 
  headers: true, 
  converters: lambda{|s| s.gsub(',','').to_i ? s && s[0] =~ /\d/ : s}) do |row|
  TownHealthRecords.find_or_initialize_by(geography: row['geography']) do |thr|
    thr.population = row['population']
    save!
  end
end