Communities adjacent to the polluted Tijuana River can now check both the air around them for contamination before they decide to venture outdoors.
The region’s air pollution cops just released an air quality tracking and alert system designed to protect the most sensitive populations from hydrogen sulfide, a gas that can become toxic commonly produced by sewage (which pollutes the river) or oil refineries. The board of the Air Pollution Control District requested an air quality alert system for the gas back in September after local university researchers publicized what they said were extremely dangerous levels of hydrogen sulfide emanating from the river.
Residents can sign up to get alerts from the new system by email showing whether the air each day is contaminated by hydrogen sulfide.
The new alert network looks similar to one created by the county to monitor Tijuana River pollution in the ocean along South Bay beaches. The water is tested each day by the county which then issues public recommendations on whether it’s safe to enter the water.
Two air quality sensors in Nestor and San Ysidro track levels of the gas which are then translated into one of four risk categories and recommended action people should take.
Green means there’s gas but people won’t smell it. Yellow means people sensitive to the gas’ smell (those with asthma, children, etc.) should limit outdoor activities if the smell bothers them. Orange means shut windows and doors in your home to prevent the smell from intruding, then open the home up again when the smells go away, or seek medical care if side-effects worry you. Finally purple means the level of gas is so high, people could experience adverse, lasting health effects and government emergency responders will let people know whether to shelter in place or evacuate.
Digging a bit deeper into the numbers behind each gas exposure threshold shows that San Diego’s air pollution cops are handling hydrogen sulfide very cautiously.
A level of 27,000 parts per billion or higher triggers that purple level. While that seems high, exposure standards set by air regulators like the California Air Resources Board say levels generally have to reach 50,000 parts per billion to 300,000 parts per billion or higher to trigger very serious health impacts – even death. Typically workers in industrial settings (someone working at a sewage plant or at an oil refinery) only run into those kinds of levels.
Generally people start to smell hydrogen sulfide around 30 parts per billion (or thirty particles out of one billion particles of air) – that translates to the yellow or orange alert category, the middle two out of four. Just smelling the gas doesn’t typically pose a serious health risk, but that’s a level when the smell can trigger physiological responses like nausea or headaches in some people.
“These levels are written to protect the most sensitive individuals who may have preexisting health conditions and provide guidance for children who may be more impacted by strong odors,” said Paula Forbis, San Diego’s air pollution control officer.
Forty percent of people in the general population would find 30 parts per billion extremely bothersome, Forbis said.
Forbis said her office built these guidelines based on recommendations from the U.S. Environmental Protection Agency. The EPA says people who are more sensitive to the gas could experience health problems that last longer than when they were just smelling the gas for an hour at a level of 27,000 parts per billion.
Another key new element to these guidelines: If sensors read gas levels at 200 parts per billion for an hour, that triggers the air pollution cops to notify the county’s public and environmental health departments as well as emergency responders.
“Our South Bay communities have long suffered the consequences of poor air quality, and they deserve timely, accurate information to make decisions that impact their daily lives, businesses, and schools,” said San Diego County Supervisor Board Chair Nora Vargas.
Correction: An earlier version of this article incorrectly stated the unit conversion for the EPA standard. It’s at a level of 27,000 parts per billion of hydrogen sulfide that a sensitive person could begin to experience health problems.
Leaded aviation fuel emissions are increasing. Although a new state law will restrict its use, it will not take effect for at least 5 years and many more children will suffer from lead exposure.
“The science is clear: exposure to lead can cause irreversible and life-long health effects in children,” said EPA Administrator Michael S. Regan. “Aircraft that use leaded fuel are the dominant source of lead emissions in our air.