Air pollution is a growing problem that in recent days has reached our own backyard.\r\n\r\nBecause of the bushfires in surrounding areas, Sydney's air has been ranked the ninth worst in the world. It\u2019s not the first time in history it\u2019s happened but it has been the longest streak in recorded history and akin to smoking between four and 10 cigarettes.\r\n\r\nThe World Health Organisation estimates 7 million people are killed annually by air pollution and nine out of 10 people globally breathe air with high levels of pollutants.\r\n\r\nFor people suffering from respiratory diseases it is even worse. These are diseases affecting the airway such as asthma, bronchitis and lung cancer.\r\n\r\nAnd Climate change is expected to decimate our air even further. Rhinomed (ASX:RNO) managing director Michael Johnson told Stockhead this was commonly overlooked.\r\n\r\n"'When people think about climate change they often think about increases in temperature or a rise in sea level," he said. "This is both simplistic and naive.\r\n\r\n"Climate change will lead to a significant range of changes across the environment such as a decline in air quality, changes in humidity [and] changes in the lengths of seasons.\r\n\r\n"These will all lead to a change in the type of diseases and pathogens that we would normally be exposed to."\r\n\r\nAs with other problems in society, such as the opiod crisis and water pollution, there are ASX small caps seeking to tackle it head on.\r\n\r\n\r\n\r\n \r\nPurifying air\r\nBut there is just one ASX small cap seeking to tackle dirty air head on, the remainder are focused on helping sufferers of respiratory diseases.\r\n\r\nPurifloh (ASX:PO3) was at 47c in November last year but now sits as $4.32 - a gain of over 800 per cent. The run was triggered by an American investor buying a stake at a hefty premium to its then price.\r\n\r\n\ufeff \r\n\r\nThis company's technology generates radicles (atoms) which can clean dirty surfaces, water and air by killing contaminants.\r\n\r\nYou may be disappointed to hear it is only focused on the indoors - for now. But the company believes we spend 90 per cent of out time indoors and air pollutants can be two to five times higher.\r\n\r\n \r\nHelping respiratory disease sufferers\r\nResApp (ASX:RAP) helps to manage diseases with diagnostic smart phone apps. Essentially it can tell by someone coughing into their smart phone.\r\n\r\nIn April, a clinical trial of its adult-focused app showed positive results - 86 per cent of results were in line with clinical diagnoses.\r\n\r\nThe most recent news out of the company came a couple of weeks ago. It announced it had made it onto a tele-health platform and that 5,500 clinicians currently used it. Of all the companies in this space it has gained the most -- up 150 per cent in 12 months.\r\n\r\n \r\n\r\nOthers that have developed apps that assist respiratory disease sufferers (specifically asthma) include Respiri (ASX:RPI) and Adherium (ASX:ADR). Both companies have a self-assessment and log medication app.\r\n\r\nMedical Developments International (ASX:MVP) is 2019's other big winner having gained 78 per cent. It sells products which optimise asthma treatment including spacers, masks, peak flow meters and portable neubulisers.\r\n\r\nShareholders of Pharmaxis (ASX:PXS) are most looking forward to an imminent decision by Boehringer Ingelheim to take up its anti-NASH and diabetic retinopathy drug.\r\n\r\nBut its product pipeline includes two respiratory disease fighters -- Bronchitol, for the treatment of cystic fibrosis, and Aridol, an asthma test kit.\r\n\r\nAdAlta (ASX:AD1) has anti-fibrotic drugs including idiopathic pulmonary fibrosis - which affects the lungs.\r\n\r\nMeanwhile, one stock in the lung imaging field is Cyclopharm (ASX:CYC). Its tech is specifically designed to detect pulmonary embolus (artery blockage).\r\n\r\nNext year it will be joined on the bourse by 4dX which in October passed a major clinical trial.\r\n\r\n \r\nTackling snoring\r\nSnoring is usually considered more of an inconvenience than a health problem. But various studies in this decade, most recently by the University of Washington earlier this year, found air pollution can actually make snoring worse.\r\n\r\nRhinomed makes devices that aid with snoring by delivering more air through the nose or in Johnson's words "improve nasal respiration".\r\n\r\n"As the entry point for the airway, the nose plays a vital role in preparing air for the lungs," he explained.\r\n\r\n"The nose and upper airway humidify the air we breathe, optimise the temperature, and importantly, filter out pathogens and particulates before they hit the lungs.\r\n\r\n"We believe that the need for technology of this type will sadly only increase as our environment deteriorates and the number of people being affected increases."