Austin air is dirtier than it’s ever been, at least in our neighborhood. Whatever the official ozone readings may or may not be, this is about just plain d-i-r-t. Since the thermometer has officially recorded 100-degree temperatures at least once, we decided to open the four exterior transom lights for summer air circulation. Once the matchbook shims jamming them closed for the winter have been removed, I usually clean the sill between the glass indoors and the screen outdoors. Ordinarily, this involves brushing out a mud-dauber or two or maybe a cobweb or a yellowjacket, with practically no actual dirt. This time it was different. When I climbed up on the ladder, I could see more than spider-work and the remains of insects. There was gritty particulate matter as well as dark, almost greasy, grime that resisted a simple swipe from a duster; removal required a cloth soaked in water containing dish-detergent. Afterwards, the washrags wouldn’t rinse clean; they were discarded. The fans have been in the windows for over a week now, and their blades are as filthy after that short time as in the past they’ve been after an entire season of spring plus summer plus early fall. Is this a byproduct of the concentrated and incessant operation of all the dump trucks, debris-trailers, over-the-road 18-wheel rigs, lumber and brick deliveries, ready-mixed-concrete trucks, sod-haulers, forklifts, jackhammers, construction and excavation equipment of every size, and all the other unpleasant effects of suffering from redevelopment of close-in Austin? We know what we see on Saturdays, when only some crews are working; weekdays, we hear, are much worse. Whatever the cause, this is evidence of deterioration in air quality. If we had old-fashioned Priscilla net curtains, they’d need to be washed every week to stay white at this rate. So, breathe at your own risk.