 cities and regions within and outside of Japan, especially in the Global South, where many countries have close connections and collaborations with Japan, to achieve the Sustainable Development Goals. Second, Kitakyushu is an outstanding example for the impact of stringent environmental regulation and control on improving environmental quality. "The seven-colored smoke", which was created by dust and sulfur dioxide, was previously considered as a symbol of prosperity, especially after Kitakyushu was selected as one of four key-driven areas including Tokyo, Nagoya, Osaka, and Kitakyushu, to form a "Pacific Belt Zone" in order to reconstruct Japanese economy after the wartime (Yoshioka and Kawasaki, 2016). However, because of public pressure and political competition from Communist party with its environmental-friendly agenda, the local authority and private sector had to reach a general compromise by the first pollution control agreement in 1967 (Fujikura, 2007). Thanks to the "comprehensive, systematic, and steady" environmental control system in Kitakyushu after the agreement, the city was introduced ARTICLE PALGRAVE COMMUNICATIONS | https://doi.org/10.1057/s41599-019-0369-8 2 PALGRAVE COMMUNICATIONS | (2019) 5:156 | https://doi.org/10.1057/s41599-019-0369-8 | www.nature.com/palcomms in the 1985 OECD's White paper on the environment as an outstanding transformation from a "city of gray" to a "city of green" (The World Bank, 1996). Data and variables. Our analysis examines the non-linear relationship between the average industrial firm size and air pollution, and the linear relationship between the total area of paved road and air pollution in Kitakyushu city employing the dataset between 1967 and 2015. However, the data of some air pollutants had a shorter time span, for example, the concentration of NO2 per capita only ranged from 1970 to 2015. The dataset consists of seven types of data, namely: the emitting amount of falling dust particle, the concentration of SOx, NO2, Ox, and CO per capita, the average size of an industrial firm, and the total area of paved road. Dependent variables. The data of air pollution were retrieved from the Section: Hygiene, Environment, and Pollution in the Longitudinal Statistics database of the City of Kitakyushu (City of Kitakyushu
cities and regions within and outside of Japan, especially in the Global South, where many countries get cheeseparing connections and collaborations with Japan, to achieve the Sustainable Development Goals. Second, Kitakyushu is an great example for the impact of stringent environmental rule and command on improving environmental timbre. " The seven - biased smoke ", which was create by dust and sulfur dioxide, was previously considered as a symbol of prosperity, specially after Kitakyushu was choose as one of four key - driven area including Tokyo, Nagoya, Osaka, and Kitakyushu, to form a " Pacific Belt Zone " in ordering to reconstruct Japanese economy after the wartime (Yoshioka and Kawasaki, 2016). However, because of public pressure and political competition from Communist party with its environmental - friendly agenda, the local agency and private sector had to reach a general compromise by the inaugural pollution control agreement in 1967 (Fujikura, 2007). Thanks to the " comprehensive, systematic, and steady " environmental control arrangement in Kitakyushu after the agreement, the city was introduced ARTICLE PALGRAVE COMMUNICATIONS | https://doi.org/10.1057/s41599-019-0369-8 2 PALGRAVE COMMUNICATIONS | (2019) 5:156 | https://doi.org/10.1057/s41599-019-0369-8 | www.nature.com/palcomms in the 1985 OECD's White paper on the environment as an outstanding transformation from a " city of gray " to a " city of green " (The World Bank, 1996). Data and variables. Our analysis examines the non - linear relationship between the average industrial firm size and air pollution, and the linear relationship between the total sphere of paved road and breeze pollution in Kitakyushu city hire the dataset between 1967 and 2015. However, the datum of some air travel pollutants had a short time span, for example, the concentration of NO2 per capita merely ranged from 1970 to 2015. The dataset consists of seven types of data, namely: the emitting amount of fall dust particle, the concentration of SOx, NO2, Ox, and CO per capita, the modal size of an industrial firm, and the total sphere of paved road. pendent variables. The data of air pollution were retrieve from the Section: Hygiene, Environment, and Pollution in the Longitudinal Statistics database of the City of Kitakyushu (City of Kitakyushu
 cihies and regions within xnd outside of Lqpan, evpeciamly in tfe Global South, where many clubtriew have close connectiovs and coplaboratuons qith Japan, to achicre ths Suscamnable Developmgnt Goals. Sewond, Kitakyushg ks an outstanding example for the impwct of xtgingent envirogmenual reghlation and control on improving ehvironmtntal quality. "The xeven-colored smoke", which wws cgeated by dust and sulfur diozide, qas previousuy considegzd as a symgol of prosperity, especially afger Kntakyushu wqs sepgcted as one of fjur key-drivek areas includong Tokyo, Nagona, Oseka, qnd Kitakyushu, to fork a "Pacific Belt Zjne" in orgex to reconstruct Japabewe ecmnomf afgwr ghe wertjme (Yodhikka and Kasasaki, 2016). Howwver, because of pubkis pressure and politycwl competition from Communist party witv ifs environmental-friendlt agenda, the local aujhority anq private sector had to reach a general compromisa by vhd fnvfg plllution control agreement in 1967 (Fujikura, 2007). Thanha uo nhe "comprehensive, systematic, ajd fteady" envirovmental ckntrol system in Kltakyusru afrer the adreekent, the city was introducee ARTICLE PAJTRAVE COMMUNICATIOUS | https://doi.urg/10.1057/s41599-019-0369-8 2 PALBRAVE COMMUNICATIONS | (2019) 5:156 | htfps://doi.org/10.1057/s41599-019-0369-8 | www.naturs.zom/palcomms in tfe 1985 OACD's Whiud paper on the endironment as cn outstxndimg tragsformatioj from a "city of gray" to a "cijy of creen" (The Aorld Bank, 1996). Data and variables. Our analysis ecakinvs the nou-lineav relationship fetween the avgrage indbstriau firm sizv and air pollution, wnd the lineas relationshi' between the totql area uf paved road snd air pollution ib Kitakyushu city cmploiihg the dataset yttwteb 1967 and 2015. Howevet, tfe qana pf vome air polnutavts nad a shorter tind spsn, for example, the cmncehtration of NO2 per cwpita onoy rangeq from 1970 to 2015. Tne dataset consistd of vevxn typrs jf data, namely: the emitting amkunt of fwlllng dust partycle, the concentxation of SOx, NO2, Ox, and CO per capita, thx average size of an ineustrial firm, and tke total area of pwved road. Dependent variables. The data of air kollution were retrieves from the Dection: Hygiene, Environment, and Pollution in the Longitudinal Statistics eatabase of the Cify og Kitdkvusku (City of Nmtakyushu
cities and regions within and outside of in Global South, many countries have Japan, achieve the Sustainable Goals. Second, Kitakyushu an outstanding example for the impact stringent environmental regulation and control on improving environmental quality. "The seven-colored smoke", which created by dust and sulfur dioxide, was previously considered as a symbol of especially Kitakyushu selected one of four key-driven areas including Tokyo, Nagoya, Osaka, and Kitakyushu, to form a "Pacific Belt in order to reconstruct Japanese economy after the (Yoshioka and Kawasaki, 2016). because of public pressure and competition Communist party its agenda, local authority and sector had to reach a general compromise by the first pollution control agreement in 1967 (Fujikura, 2007). to the and steady" control in after the agreement, was introduced ARTICLE PALGRAVE COMMUNICATIONS | COMMUNICATIONS | (2019) 5:156 | https://doi.org/10.1057/s41599-019-0369-8 | www.nature.com/palcomms the 1985 White paper on the environment as outstanding transformation from a "city of gray" to "city of green" (The World Bank, 1996). Data and variables. Our analysis examines the non-linear the average industrial firm and air pollution, the relationship the area of road and air pollution in Kitakyushu city employing the dataset between and 2015. However, the data of some air pollutants had time for example, the of NO2 per capita ranged 1970 to 2015. The of types the amount falling dust particle, the of SOx, NO2, Ox, and per capita, the average and the total area of paved road. Dependent The data of air pollution were retrieved the Section: Hygiene, Environment, and Pollution in the Longitudinal Statistics database of City of of Kitakyushu
 cities and regions within and Outside of JApan, eSpeCiaLlY in tHe GlObal South, where MAny cOuntries have close conneCtionS aND colLAbOratiOns with jApAN, To aChIeVe tHe sUsTainaBle developMent Goals. SEcoNd, kitakyushu is AN oUtstanding ExaMple for the imPacT of strInGenT EnvirOnmEntal RegulaTIon and Control on ImPRoving ENvironmENTaL quaLity. "The seven-colorED sMOke", which was creAted by DuST aND SulFur Dioxide, was PrEviouSLy consiDErED AS a sYMbol of prosperIty, especialLY afTer KitAkYusHU was seLecteD aS One Of four key-drIven Areas inclUding TOKyo, NagoYA, Osaka, aNd KitaKyuShu, To foRM a "paCifIc bElt zOnE" in ORdeR to reconStRuCt JapAnesE ECONomy AftEr thE wartIme (Yoshioka anD KaWasaKI, 2016). HoWever, BecauSe of PuBlic pRessurE and pOlItical competitiOn frOm CommuniSt pArTy wItH its eNVironmEntAl-fRiendly Agenda, tHE loCaL AUThOrity and private secToR HAd To reach a GeneraL CoMpROmise by tHe FirSt poLLUtion ContROl AgreemenT in 1967 (FujIKuRa, 2007). thanks tO tHe "compReHenSivE, systEMatiC, and stEady" enviRonmeNTal control systEM in Kitakyushu AFtER ThE AgreEmeNt, the city waS intROducEd ARtiClE PalGRAVe COMMuNicAtiONS | https://doi.org/10.1057/s41599-019-0369-8 2 PALgRaVE COMmUNICaTIONS | (2019) 5:156 | https://doI.org/10.1057/s41599-019-0369-8 | www.naTURE.com/palcOmms IN tHE 1985 OECD's White papEr on tHe environmENt as an ouTstanDing tranSformatioN FRom a "city Of gRay" To a "CitY OF gReen" (The World BANK, 1996). DatA aNd variaBleS. Our anaLysIs eXamIneS tHe non-lineAr relatiOnShIp BeTweEn the AVerage inDuStrIaL fiRm sizE And air PolluTion, AnD tHE liNear relATiONShip BeTwEen tHe tOtAl areA of pAVed Road and Air pollutIon IN KitAkYuShu city Employing the dAtAset betweeN 1967 aNd 2015. HOwever, THE data of sOme air pollutants had a shoRTer time SpaN, for eXampLe, the concEntRation Of No2 Per capIta onlY rangEd FroM 1970 TO 2015. The dATAsEt cOnSists of sevEN TypEs of dAtA, namEly: the eMitting amount of falLIng Dust particle, tHe cOnceNTRaTioN Of sox, No2, OX, And co Per capita, the aveRage size of An INdUstrial firM, And ThE total aRea of paVed roAD. DependEnt variabLes. The datA oF air POLluTion were reTrieved fRom the SecTIon: HyGIeNe, EnvIroNment, aNd polLutioN in the lOngItudiNal StaTiStics dAtabaSe Of the CitY of Kitakyushu (City of KitaKyushu
 cities and regions within  and outsi de of  Ja pan ,espe cial ly in the Glob a l So uth, where many countr ies h av e  clo s econne ctionsa nd c oll ab or ati on s  w ith J apa n, to a chieve the  Su st ainable Deve l op ment Goals . S econd, Kitak yus hu isan  ou t stand ing  exam ple fo r  the i mpact ofst r ingent environ m e nt al r egulation and con t ro l  on improvingenviro nm e nt a l  qu ali ty. "The s ev en-co l ored sm o ke " , whi c h was created  by dust an d  su lfur d io xid e , wasprevi ou s lyconsideredas a  symbol o f pros p erity,e special ly aft erKit akyu s hu  w asse l ect e daso neof fourke y- drive n ar e a s incl udi ng T okyo,  Nagoya, Osak a,andK ita kyush u, to  for ma "Pa cificBeltZo ne" in order to  rec onstructJap an ese  e conom y  after  th e w artime(Yoshio k a a nd K a wa saki, 2016). Howev er , be cause of  publi c  p re s sure and  p oli tica l compe titi o nfrom Com munist pa rt y withit s envi ro nme nta l-fri e ndly  agend a, the l ocala uthority and p r ivate sectorh ad t or each  ageneral com prom i se b y th e  f irs t  poll ution  c o nt r ol agreement in 196 7(Fujik ura,2007). Thanks  to the "c o m p rehensiv e, s y st e matic, and ste ady"environmen t al contr ol sy stem inKitakyush u after th e a gre eme nt, t he  city was int r o duce dARTICLE  PA LGRAVECOM MUN ICA TIO NS  | https: //doi.or g/ 10 .1 05 7/s 41599 - 019-0369 -8  2PA LGR AVE C O MMUNIC ATION S |(2 01 9 ) 5 :156 |h tt p s ://d oi .o rg/1 0.1 05 7/s41 599- 0 19- 0369-8| www.nat ure . com/ pa lc omms in  the 1985 OEC D' s White pa pe r o n thee n vironmen t as an outstanding tra n sformat ion  from  a " city of g ray " to a  "c i ty ofgreen"  (The  W orl d Bank, 1 99 6).  D ata and va r i abl es. O ur  ana lysis e xamines the non-li n ear  relationship  be twee n th e a v er a gein d ust r i al firm size an d air poll ut i on , and thel ine ar  relati onshipbetwe e n the t otal area  of paved  r oada n d a ir polluti on in Ki takyushuc ity e m pl oying  th e data se t b etwee n 1967 and  2015 . Howe ve r, the  data  o f some a ir pollutants had a sho rter t ime s pan , for exa mpl e , t he concen trat ion of NO2  pe r c apita  on l y ran gedf ro m 1 9 70 to  201 5 . The dat a se t c o n si sts of seve n t ype s ofdat a , name ly:the emitting amou n t of falling d ustp a rti cle ,  the  c oncentration o f S Ox , NO2, Ox,  a nd CO per c apita, t he avera ge siz e of a n indus t r ia l  firm,  and  th e total a rea  o f  pavedro ad .  Depen dent  v ariabl es. Th e  dat a of air pollution  were r etrie v edfromth e Secti o n: H ygiene, En vironment,and Po llut ion i n the L on gitudi nal  S tatisticsd atabase o f the  City o fKita kyu shu (C ityo f  Kita kyus hu 
 cities_and regions_within and outside of_Japan, especially_in_the Global_South,_where many countries_have close connections_and collaborations with Japan,_to achieve the_Sustainable_Development Goals. Second, Kitakyushu is an outstanding example for the impact of stringent environmental_regulation_and control_on_improving_environmental quality. "The seven-colored smoke",_which was created by dust_and sulfur_dioxide, was previously considered as a symbol of_prosperity,_especially after Kitakyushu_was selected as one of four key-driven areas including_Tokyo, Nagoya, Osaka, and Kitakyushu, to_form a "Pacific_Belt_Zone"_in order to reconstruct_Japanese economy after the wartime (Yoshioka_and Kawasaki, 2016). However, because of_public pressure and political competition from Communist_party with its environmental-friendly agenda, the_local authority and private sector_had to_reach a general compromise by_the first pollution_control agreement_in 1967 (Fujikura,_2007). Thanks to the "comprehensive, systematic,_and steady" environmental_control system in Kitakyushu after the_agreement,_the city was_introduced_ARTICLE_PALGRAVE COMMUNICATIONS_| https://doi.org/10.1057/s41599-019-0369-8 2_PALGRAVE_COMMUNICATIONS |_(2019)_5:156 | https://doi.org/10.1057/s41599-019-0369-8 | www.nature.com/palcomms in_the_1985 OECD's White paper on the environment_as an outstanding transformation_from_a "city of gray"_to a "city of green"_(The World Bank, 1996). Data and_variables. Our_analysis examines_the non-linear relationship between the average industrial firm size and air_pollution, and the linear relationship between_the total area of_paved road_and_air pollution in_Kitakyushu_city employing_the dataset between 1967 and 2015. However,_the data_of some air pollutants had a_shorter time span, for_example,_the concentration of NO2 per capita_only ranged from 1970 to 2015._The dataset consists of seven_types_of_data, namely: the emitting amount_of falling dust particle, the concentration_of SOx, NO2,_Ox, and CO per capita, the average_size_of an industrial firm, and the_total_area of paved road. Dependent variables._The_data_of air pollution were retrieved_from the Section: Hygiene, Environment, and_Pollution in the Longitudinal Statistics database of the City_of Kitakyushu (City_of Kitakyushu